Media playback system with virtual line-in

ABSTRACT

Example systems and techniques disclosed herein facilitate interoperability between different media playback systems referred to herein as a virtual line-in (VLI) media playback system and a native playback system. When a VLI session is created by a VLI sender, a first native playback device can join a VLI group as a VLI receiver. As a VLI receiver, the first native playback device receives audio content and playback commands from the VLI sender to facilitate synchronous playback with other VLI receivers. At the same time, this native playback device can concurrently operate as a native domain group coordinator of a native domain synchrony group. As the native domain group coordinator, the native playback device translates VLI domain audio, control, and timing signals into the native domain and distributes such signals to native domain group members. In this way, the native domain group members can synchronize their playback with the VLI group.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. § 119 of U.S.provisional App. No. 62/672,020 filed on May 15, 2018, entitled “MediaPlayback System with Virtual Line-In,” which is incorporated herein byreference in its entirety.

FIELD OF THE DISCLOSURE

The disclosure is related to consumer goods and, more particularly, tomethods, systems, products, features, services, and other elementsdirected to media playback or some aspect thereof.

BACKGROUND

Options for accessing and listening to digital audio in an out-loudsetting were limited until in 2003, when SONOS, Inc. filed for one ofits first patent applications, entitled “Method for Synchronizing AudioPlayback between Multiple Networked Devices,” and began offering a mediaplayback system for sale in 2005. The Sonos Wireless HiFi System enablespeople to experience music from many sources via one or more networkedplayback devices. Through a software control application installed on asmartphone, tablet, or computer, one can play what he or she wants inany room that has a networked playback device. Additionally, using thecontroller, for example, different songs can be streamed to each roomwith a playback device, rooms can be grouped together for synchronousplayback, or the same song can be heard in all rooms synchronously.

Given the ever growing interest in digital media, there continues to bea need to develop consumer-accessible technologies to further enhancethe listening experience.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, aspects, and advantages of the presently disclosed technologymay be better understood with regard to the following description,appended claims, and accompanying drawings where:

FIG. 1 shows an example media playback system configuration in whichcertain embodiments may be practiced;

FIG. 2 shows a functional block diagram of an example playback device inaccordance with aspects of the disclosure;

FIG. 3 shows a functional block diagram of an example control device inaccordance with aspects of the disclosure;

FIG. 4 shows a functional block diagram of an example virtual line-indevice in accordance with aspects of the disclosure.

FIGS. 5A and 5B are example native control interfaces in accordance withaspects of the disclosure;

FIG. 6 is an example virtual line-in (VLI) control interface inaccordance with aspects of the disclosure;

FIGS. 7A, 7B, 7C, and 7D are example functional block diagramscorresponding to example virtual line-in configurations in accordancewith aspects of the disclosure;

FIGS. 8A, 8B, and 8C are example functional block diagrams correspondingto example virtual line-in timing configurations in accordance withaspects of the disclosure; and

FIGS. 9A and 9B are example functional block diagrams corresponding toexample virtual line-in timing configurations in accordance with aspectsof the disclosure.

FIG. 10 shows a technique to distribute control and audio signals withVLI and native domain groups, according to example implementations.

FIG. 11 shows a technique to distribute timing signals with VLI andnative domain groups, according to example implementations.

The drawings are for the purpose of illustrating example embodiments,but it is understood that the inventions are not limited to thearrangements and instrumentality shown in the drawings.

DETAILED DESCRIPTION I. Overview

Example systems and techniques disclosed herein facilitateinteroperability between different media playback systems. Whileplayback devices of different media playback systems may implement somesimilar features, such playback devices might not be compatible with oneanother. For instance, while playback devices of respective mediaplayback systems may each support forming playback groups with playbackdevices of the same media playback system, playback devices of differentmedia playback systems may be unable to form playback groups with oneanother. Such incompatibility may be inherent as different mediaplayback systems may implement similar features in different ways. Yet,some users may benefit from interoperability between devices ofdifferent media playback systems.

Within examples, to enable interoperability between a first mediaplayback system and a second media playback system, the first mediaplayback system may implement a virtual line-in to interface with thesecond media playback system. The second media playback system, whichmay be a third-party media playback system (i.e. a media playback systemproduced by a different manufacturer than the first media playbacksystem, which may be referred to as a first-party media playbacksystem), may make certain information available via an applicationprogramming interface. Such information may include control and timingsignals, as well as the content itself. However, in various examplesdisclosed herein, such control and timing signals are provided by thesecond media playback system in forms used by the second media playbacksystem, which are different from forms utilized by the first mediaplayback system. Forms used by the second media playback system arereferred to herein as VLI domain (e.g., VLI timing domain, VLI controldomain, etc.) while forms used by the first media playback system arereferred to herein as native domain (e.g., native timing domain, nativecontrol domain, etc.)

Yet, in examples in which information in this VLI domain is the onlyinformation made available by the second media playback system, thefirst media playback system is dependent upon this VLI domaininformation to enable interoperability. That is, the first mediaplayback system cannot force the second media playback system to operatein the native domain of the first media playback system, but mustinstead adapt to the VLI domain of the second media playback system. Inone aspect, the first media playback system may treat the VLI domaininformation provided by the second media playback system as an audiosource, or virtual line-in. In various embodiments described below, theVLI domain information may include information from an analog or digitalaudio signal similar to that received via a more traditional line-ininterface, but further includes, e.g., timing information forsynchronizing playback and/or other operations between the first and thesecond playback systems and/or control information.

For example, to synchronize playback among multiple playback devices ina synchrony group, the first media playback system may designate aparticular playback device of the synchrony group as a groupcoordinator. The group coordinator distributes native domain playbackand timing information with the other playback devices of the synchronygroup (i.e., the group members). The group members match theirrespective native domain clocks (either physically or logically) to theclock of the group coordinator to facilitate synchronous playback.

The second media playback system may also have a feature of synchronousplayback among multiple playback devices in a synchrony group, butimplement this feature in a different way. For instance, the VLI timingdomain of the second media playback system might use a differentprotocol (such as real-time transport protocol (RTP) or precision timeprotocol (PTP)) than the native timing domain of the first mediaplayback system (which might use simplified network time protocol(SNTP), among others). As such, the second media playback system mightonly make available timing information in a domain that is differentfrom the timing domain used by the first media playback system. Thesedistinct timing domains are inherently not synchronized with oneanother.

In accordance with embodiments of the disclosure, to facilitateinteroperability, one or more playback devices of the first mediaplayback system may adopt the VLI timing domain of the second mediaplayback system in a way that enables the creation of a VLI synchronygroup. For instance, if the second media playback system uses PTP, theseplayback devices of the first media playback system may join thehierarchical master-slave architecture of that protocol as implementedwithin the second playback device by implementing PTP servers and/orclients (i.e., VLI domain timing servers/clients). For example, in somecases, these playback devices of the first media playback may eachimplement a PTP server and receive timing information from a PTP serveron a PTP master within the second media playback system. Alternatively,a particular playback device of the first media playback system mayoperate as the PTP master (or more generally, “a timing master”) of aVLI group. Yet, to retain compatibility with other playback devices ofthe first media playback system, these playback devices concurrentlymaintain one or more clocks in the native timing domain, which may bematched (either physically or logically) to the VLI time domain.

Within examples, each media playback system may utilize one or morecontrol interfaces for controlling playback and other functions of theplayback devices in the first and second respective systems. Forinstance, the first media playback system may implement playback controlvia a native controller application or “native controller” (i.e., asoftware controller) running on a smartphone, tablet, or PC, whichexchanges native domain control signaling with playback devices of thefirst media playback system via a network. Likewise, a VLI controllerapplication or “VLI controller” (i.e., a software controller) on one ormore devices of the second media playback system may control playback bythe devices of the second media playback system. Each controller maypresent a graphical user interface on one or more displays with variousplayback controls such as transport controls (e.g., play, pause, andskip forward and backward), volume controls, and media library controls,among other examples to facilitate control of playback by the variousdevices of each system. Moreover, example playback devices of the firstand/or second media playback systems may include their own respectivecontrol interfaces (e.g., a playback device may include physicaltransport controls on its housing).

To create a VLI group, a user may select one or more playback devices ofthe first and/or second media playback systems using a VLI controlinterface on a given VLI device. Example VLI control interfaces includea graphical user interface (GUI) of a VLI controller displayed on a VLIdevice or a voice user interface (VUI) implemented using microphones ona VLI device. Upon selecting one or more playback devices of the firstand/or second media playback systems, a VLI session is created. Thegiven VLI device that created the VLI group and initiated the VLIsession becomes the “VLI sender,” which provides audio and controlinformation to playback devices of the first media playback system whichare in the VLI group. These playback devices are referred to as VLIreceivers. While operating as the “source of truth” within the VLI groupfor audio and control information, the VLI sender is not necessarily the“source of truth” for timing information within the VLI group.

Generally, during a VLI session (when the VLI receiver(s) are treatingthe VLI sender as a virtual line-in), VLI domain control commandsreceived via a control interface of the VLI sender are passed throughthe virtual line-in and transmitted to each VLI receiver of the VLIgroup. In addition, audio is sourced by the VLI sender (either fromstorage on the device or from a network location) and distributed toeach of the VLI receivers.

The playback and control devices of the first media playback systemretain their native domain audio and control signaling concurrently withthe VLI signaling. In various embodiments, maintaining native domainsignaling enables devices of the first media playback system that arenot within the VLI group to interact with devices of the first mediaplayback system that are within the VLI group. In some instances,concurrent VLI and native domain signaling enables compatibility of VLIreceivers with certain devices of the first media playback system thatmight not support becoming VLI receivers or handling VLI signaling, suchas legacy devices, which might have hardware incompatibilities.

In some examples, limited two-way control originating within the nativecontrol domain, which may be referred to as “backchannel control,” ispossible. The extent of this backchannel control may be generallyrestricted or limited by the control functions available over the API ofthe second media playback system. For instance, the second mediaplayback system may publish API functions corresponding to transportcontrols, such as play, pause, skip forward, skip backward, etc. When anative domain transport control command is received via a native domaincontrol interface on the VLI receiver, the VLI receiver converts thenative domain transport control command to a VLI domain transportcontrol and transmits the VLI domain transport control back to the VLIsender. If a native domain transport control command is received via anative domain control interface on a native domain control device orgroup member, the native domain transport control command is transmittedto the VLI receiver, which converts the native domain transport controlcommand to a VLI domain transport control and transmits the VLI domaintransport control back to the VLI sender. In this manner, native domaincontrol may be at least partially retained during a VLI session.

As noted above, example techniques may involve a virtual line-in. Eachof these example implementations may be embodied as a method, a deviceconfigured to carry out the implementation, a system of devicesconfigured to carry out the implementation, or a non-transitorycomputer-readable medium containing instructions that are executable byone or more processors to carry out the implementation, among otherexamples. It will be understood by one of ordinary skill in the art thatthis disclosure includes numerous other embodiments, includingcombinations of the example features described herein. Further, anyexample operation described as being performed by a given device toillustrate a technique may be performed by any suitable devices,including the devices described herein. Yet further, any device maycause another device to perform any of the operations described herein.

While some examples described herein may refer to functions performed bygiven actors such as “users” and/or other entities, it should beunderstood that this description is for purposes of explanation only.The claims should not be interpreted to require action by any suchexample actor unless explicitly required by the language of the claimsthemselves.

Moreover, some functions are described herein as being performed “basedon” or “in response to” another element or function. “Based on” shouldbe understood that one element or function is related to anotherfunction or element. “In response to” should be understood that oneelement or function is a necessary result of another function orelement. For the sake of brevity, functions are generally described asbeing based on another function when a functional link exists; however,such disclosure should be understood as disclosing either type offunctional relationship.

II. Example Operating Environment

FIG. 1 illustrates an example configuration of a system 100 in which oneor more embodiments disclosed herein may be implemented. The system 100as shown is associated with an example home environment having severalrooms and spaces, such as for example, an office, a dining room, and aliving room. Within these rooms and spaces, the system 100 includes twomedia playback systems, referred to herein as a native media playbacksystem and a VLI media playback system. The native media playback systemincludes playback devices 102 (identified individually as playbackdevices 102 a-102 i), and control devices 103 a and 103 b (collectively“control devices 103”). The VLI media playback system includes VLIdevices 104 (identified individually as VLI devices 104 a-104 e), eachof which may include control and/or playback functionality. In someembodiments, one or more of the VLI devices, such as mobile and laptopdevices 104 d and 104 e can be configured to concurrently run softwareof a VLI controller and software for a native controller, which enablesusers to select between different control interfaces using the samedevice.

Referring now to the native media playback system, the various playbackdevices 102 and other network devices, such as one or more of thecontrol devices 103 configured to run the native API software, of thenative media playback system may be coupled to one another viapoint-to-point connections and/or over other connections, which may bewired and/or wireless, via a LAN including a network router 106. Forexample, the playback device 102 g (designated as “Left”) may have apoint-to-point connection with the playback device 102 a (designated as“Right”). In one embodiment, the Left playback device 102 g maycommunicate over the point-to-point connection with the Right playbackdevice 102 a. In a related embodiment, the Left playback device 102 gmay communicate with other network devices via the point-to-pointconnection and/or other connections via the LAN.

The network router 106 may be coupled to one or more remote computingdevice(s) 105 via a wide area network (WAN) 107. In some embodiments,the remote computing device(s) 105 may be cloud servers. The remotecomputing device(s) 105 may be configured to interact with the system100 in various ways. For example, the remote computing device(s) may beconfigured to facilitate streaming and controlling playback of mediacontent, such as audio, in the home environment, perhaps as part ofproviding a streaming audio service via WAN 107. In some examples, theremote computing device(s) 105 may be representative of cloud serversfrom multiple services, perhaps operated by different entities.

Further aspects relating to the different components of the examplesystem 100 and how the different components may interact to provide auser with a media experience may be found in the following sections.While discussions herein may generally refer to the example system 100,technologies described herein are not limited to applications within,among other things, the home environment as shown in FIG. 1. Forinstance, the technologies described herein may be useful in other homeenvironment configurations comprising more or fewer of any of theplayback and/or control devices of the native media playback system. Inaddition, the technologies described herein may be useful in other homeenvironment configurations comprising more or fewer of any of the VLIdevices 104 of the VLI media playback system. Additionally, thetechnologies described herein may be useful in environments wheremulti-zone audio may be desired, such as, for example, a commercialsetting like a restaurant, mall or airport, a vehicle like a sportsutility vehicle (SUV), bus or car, a ship or boat, an airplane, and soon.

a. Example Playback Devices

FIG. 2 is a functional block diagram illustrating certain aspects of aselected one of the playback devices 102 shown in FIG. 1. As shown, sucha playback device may include a processor 212, software components 214,memory 216, audio processing components 218, audio amplifier(s) 220,speaker(s) 222, microphone(s) 224, and a network interface 230 includingwireless interface(s) 232 and wired interface(s) 234. In someembodiments, a playback device might not include the speaker(s) 222, butrather a speaker interface for connecting the playback device toexternal speakers. In certain embodiments, the playback device mayinclude neither the speaker(s) 222 nor the audio amplifier(s) 222, butrather a line-out interface for connecting a playback device to anexternal audio amplifier or audio-visual receiver. The playback deviceincludes a housing 238 carrying its constituent components.

A playback device may further include a user interface 226. The userinterface 226 may facilitate user interactions independent of or inconjunction with one or more of the control devices 104 (FIG. 1). Invarious embodiments, the user interface 226 includes one or more ofphysical buttons and/or graphical user interfaces provided on touchsensitive screen(s) and/or surface(s), among other possibilities, for auser to directly provide input. The user interface 226 may furtherinclude one or more of lights and the speaker(s) to provide visualand/or audio feedback to a user.

In some embodiments, the processor 212 may be a clock-driven computingcomponent configured to process input data according to instructionsstored in the memory 216. The memory 216 may be a tangiblecomputer-readable medium configured to store instructions executable bythe processor 212. For example, the memory 216 may be data storage thatcan be loaded with one or more of the software components 214 executableby the processor 212 to achieve certain functions. In one example, thefunctions may involve a playback device retrieving audio data from anaudio source or another playback device. In another example, thefunctions may involve a playback device sending audio data to anotherdevice on a network. In yet another example, the functions may involvepairing of a playback device with one or more other playback devices tocreate a multi-channel audio environment.

Certain functions may involve a playback device synchronizing playbackof audio content with one or more other playback devices. Duringsynchronous playback, a listener may not perceive time-delay differencesbetween playback of the audio content by the synchronized playbackdevices. U.S. Pat. No. 8,234,395 filed Apr. 4, 2004, and titled “Systemand method for synchronizing operations among a plurality ofindependently clocked digital data processing devices,” which is herebyincorporated by reference in its entirety, provides in more detail someexamples for audio playback synchronization among playback devices inthe native domain.

The audio processing components 218 may include one or moredigital-to-analog converters (DAC), an audio preprocessing component, anaudio enhancement component or a digital signal processor (DSP), and soon. In some embodiments, one or more of the audio processing components218 may be a subcomponent of the processor 212. In one example, audiocontent may be processed and/or intentionally altered by the audioprocessing components 218 to produce audio signals. The produced audiosignals may then be provided to the audio amplifier(s) 210 foramplification and playback through speaker(s) 212. Particularly, theaudio amplifier(s) 210 may include devices configured to amplify audiosignals to a level for driving one or more of the speakers 212. Thespeaker(s) 212 may include an individual transducer (e.g., a “driver”)or a complete speaker system involving an enclosure with one or moredrivers. A particular driver of the speaker(s) 212 may include, forexample, a subwoofer (e.g., for low frequencies), a mid-range driver(e.g., for middle frequencies), and/or a tweeter (e.g., for highfrequencies). In some cases, each transducer in the one or more speakers212 may be driven by an individual corresponding audio amplifier of theaudio amplifier(s) 210. In addition to producing analog signals forplayback, the audio processing components 208 may be configured toprocess audio content to be sent to one or more other playback devicesfor playback.

Audio content to be processed and/or played back by the playback device202 may be received from an external source, such as via an audioline-in input connection (e.g., an auto-detecting 3.5 mm audio line-inconnection) or the network interface 230. During a VLI session, audio istransmitted from a VLI sender of the VLI system to the VLI receiverusing the network interface 230. Such a VLI sender may be, for example,one of the VLI devices 104 (FIG. 1) or one of the control devices 103(FIG. 1) running the VLI software.

The network interface 230 may be configured to facilitate a data flowbetween a playback device and one or more other devices on a datanetwork. As such, a playback device may be configured to receive audiocontent over the data network from one or more other playback devices incommunication with a playback device, network devices within a localarea network, or audio content sources over a wide area network such asthe Internet. In one example, the audio content and other signalstransmitted and received by a playback device may be transmitted in theform of digital packet data containing an Internet Protocol (IP)-basedsource address and IP-based destination addresses. In such a case, thenetwork interface 230 may be configured to parse the digital packet datasuch that the data destined for a playback device is properly receivedand processed by the playback device.

As shown, the network interface 230 may include wireless interface(s)232 and wired interface(s) 234. The wireless interface(s) 232 mayprovide network interface functions for a playback device to wirelesslycommunicate with other devices (e.g., other playback device(s),speaker(s), receiver(s), network device(s), control device(s) within adata network the playback device is associated with) in accordance witha communication protocol (e.g., any wireless standard including IEEE802.11a, 802.11b, 802.11g, 802.11n, 802.11ac, 802.15, 4G mobilecommunication standard, and so on). The wired interface(s) 234 mayprovide network interface functions for a playback device to communicateover a wired connection with other devices in accordance with acommunication protocol (e.g., IEEE 802.3). While the network interface230 shown in FIG. 2 includes both wireless interface(s) 232 and wiredinterface(s) 234, the network interface 230 might include only wirelessinterface(s) or only wired interface(s) in various examples.

By way of illustration, SONOS, Inc. presently offers (or has offered)for sale certain playback devices including a “PLAY:1,” “PLAY:3,”“PLAY:5,” “PLAYBAR,” “PLAYBASE,” “BEAM,” “CONNECT:AMP,” “CONNECT,” and“SUB.” Any other past, present, and/or future playback devices mayadditionally or alternatively be used to implement the playback devicesof example embodiments disclosed herein. Additionally, it is understoodthat a playback device is not limited to the example illustrated in FIG.2 or to the SONOS product offerings. For example, a playback device mayinclude a wired or wireless headphone. In another example, a playbackdevice may include or interact with a docking station for personalmobile media playback devices. In yet another example, a playback devicemay be integral to another device or component such as a television, alighting fixture, or some other device for indoor or outdoor use.

b. Example Playback Zone Configurations

Referring back to the system 100 of FIG. 1, the environment may have oneor more playback zones, each with one or more playback devices 102. Thenative media playback system may be established with one or moreplayback zones, after which one or more zones may be added, or removedto arrive at the example configuration shown in FIG. 1. Each zone may begiven a name according to a different room or space such as an office,bathroom, master bedroom, bedroom, kitchen, dining room, living room,and/or balcony. In one case, a single playback zone may include multiplerooms or spaces. In another case, a single room or space may includemultiple playback zones.

In some examples, a VLI media playback system may also be establishedwith one or more playback zones. In some cases, such playback zones areestablished in different physical rooms or areas as the playback zonesof the native media playback systems. Such a configuration may avoidduplicating some functionality by having both native playback devices102 and VLI devices 104 in same physical area. Alternatively, someplayback zones of the VLI media playback system may partially or fullyoverlap with the same physical room or area as the playback zones of thenative media playback system. Such a configuration may be useful as thenative playback devices 102 and VLI devices 104 may have some differentfeatures.

Accordingly, some rooms might not have a playback device 102, but mightinstead include a VLI device 104 (or no device at all). Other roomsmight include both playback device(s) 102 and VLI device(s) 104. Forinstance, the living room may include playback devices 102 a, 102 b, 102g, and 102 i as the Living Room zone, while also including the VLIdevice 104 e. Some types of playback devices 102 and/or VLI devices 104may be portable (e.g., battery-powered) while others may draw currentfrom a wall outlet and be intended to be more or less stationary inoperation.

In some embodiments, the playback zones in the environment may bepresented to a user via a native controller. However, in the nativecontroller, the VLI devices 104 are not presented because they are notnative to the native media playback system of playback devices 102. Inadditional or alternate embodiments, some or all of the zones along withthe VLI devices 104 in the environment may be presented to a user via aVLI controller. For example, the native system may identify for the VLIsystem zones and/or playback devices 102 associated with various zonesthat are available to be controlled via the VLI controller.

As shown in FIG. 1, the Balcony, Dining Room, Kitchen, Bathroom, andOffice zones each have one playback device 102, while the Living Roomzone has multiple playback devices 102. In the Living Room zone,playback devices 102 a, 102 b, 102 j, and 102 k may be configured toplay audio content in synchrony as individual playback devices, as oneor more bonded playback devices, as one or more consolidated playbackdevices, or any combination thereof. Moreover, any playback devices 102of the native media playback system may form such groupingconfigurations. VLI devices 104 a-e may have similar features, albeitimplemented in a different manner from the native playback devices 102.For example, the VLI devices 104 b and 104 c may together form a stereopair that is represented as a single device by the VLI controller (via,e.g., a GUI presented on the display by the VLI controller) of the VLIsystem.

In one example, one or more playback zones in the environment of FIG. 1may each be playing different audio content. For instance, the user maybe grilling in the balcony zone and listening to hip hop music beingplayed by the playback device 102 c while another user may be preparingfood in the kitchen zone and listening to classical music being playedby the playback device 102 h. In another example, a playback zone mayplay the same audio content in synchrony with another playback zone. Forinstance, the user may be in the office zone where the playback device102 d is playing the same rock music that is being playing by playbackdevice 102 c in the balcony zone. In such a case, playback devices 102 cand 102 d may be playing the rock music in synchrony such that the usermay seamlessly (or at least substantially seamlessly) enjoy the audiocontent that is being played out-loud while moving between differentplayback zones. Synchronization among playback zones may be achieved ina manner similar to that of synchronization among playback devices, asdescribed in previously referenced U.S. Pat. No. 8,234,395.

As suggested above, the zone configurations of the media playback system100 may be dynamically modified, and in some embodiments, the mediaplayback system 100 supports numerous configurations. For instance, if auser physically moves one or more playback devices to or from a zone,the media playback system 100 may be reconfigured to accommodate thechange(s). For instance, if the user physically moves the playbackdevice 102 c from the balcony zone to the office zone, the office zonemay now include both the playback device 102 d and the playback device102 c. The playback device 102 may be paired or grouped with the officezone and/or renamed if so desired via a control device such as thecontrol devices 103 a and 103 b. On the other hand, if the one or moreplayback devices are moved to a particular area in the home environmentthat is not already a playback zone, a new playback zone may be createdfor the particular area.

Further, in various examples, one or more of the playback devices 102may synchronously play back audio with one or more of the VLI devices104 even though the VLI devices 104 do not form part of the nativesystem of playback devices 102. For instance, in the above example inwhich the playback device 102 c is playing the rock music in the office,the VLI device 104 d in the office may also be selected (using, e.g.,the VLI controller) to play back the same rock music with the playbackdevice 102 c (and/or other playback devices 102). Additionally, the VLIdevice 104 d or another VLI device may initiate playback of the rockmusic, and other VLI devices 104 and/or playback devices 102 may begrouped and ungrouped for playback of the rock music in the variousrooms or spaces in the environment. As such, the VLI devices 104 mayseamlessly play back audio in a manner that the user may experience assubstantially similar to that of a native media playback systemcomprising only native domain playback devices 102.

In various implementations, different playback zones of the mediaplayback system 100 may be dynamically combined into zone groups orsplit up into individual playback zones. For instance, the dining roomzone and the kitchen zone may be combined into a zone group for a dinnerparty such that playback devices 102 i and 102 l may render audiocontent in synchrony. On the other hand, the living room zone may besplit into a television zone including playback device 102 b, and alistening zone including playback devices 102 a, 102 j, and 102 k, ifthe user wishes to listen to music in the living room space whileanother user wishes to watch television.

c. Example Control Devices

FIG. 3 is a functional block diagram illustrating certain aspects of aselected one of the control devices 103 of the media playback system 100of FIG. 1. Such control devices may also be referred to as a controllerdevice. The control device shown in FIG. 3 may include components thatare generally similar to certain components of the network devicesdescribed above, such as a processor 312, memory 316, and a networkinterface 330. The control device 103 includes a housing 338 carryingits constituent components.

The memory 316 of the control device 103 may be configured to storecontroller application software and other data associated with thenative media playback system and a user of the native media playbacksystem. The memory 316 may be loaded with one or more softwarecomponents 314 executable by the processor 312 to achieve certainfunctions, such as facilitating user access, control, and configurationof the native media playback system. The control device 103 communicateswith other network devices over the network interface 330, such as awireless interface, as described above.

The control device 103 may include a plurality of microphones 324arranged to detect sound in the environment of the control device 103.The microphones may detect voice inputs to the native media playbacksystem, process those inputs, perhaps using one or more voice assistantservices (VAS), and carry out the commands on one or more playbackdevices 102.

The control device 103 may implement various user interfaces 326, suchas control interfaces for controlling the playback devices 102 of thenative media playback system. Within examples, the control device 103may be implemented on a general purpose network device via installationof software for a native controller 327 (i.e., a native controlapplication). Example general purpose network devices include, forexample, an iPhone™, iPad™ or any other smart phone, tablet or networkdevice (e.g., a networked computer such as a PC or Mac™). The nativecontroller 327 may be implemented via a control application configuredto control the native media playback system or as features of anotherapplication, such as a control application of a streaming media service.In another example, a native controller may form part of a controldevice that is dedicated to the native media playback system, ratherthan being implemented in, e.g., an application or “app” on a generalpurpose network device. In addition or alternately, the control device103 may be implemented in a like manner as a VLI device 104 viainstallation a VLI controller 428, which is described in greater detailbelow with reference to FIG. 4. In some embodiments, the control device103 may be configured to control one or both of the native and the VLImedia playback systems via separate access over the respective nativeand VLI controllers.

Playback device control commands such as volume control and audioplayback control may also be communicated from a control device to aplayback device via the network interface 330. As suggested above,changes to configurations of the native media playback system may alsobe performed by a user using the control device. The configurationchanges may include adding/removing one or more playback devices to/froma zone, adding/removing one or more zones to/from a zone group, forminga bonded or merged player, separating one or more playback devices froma bonded or merged player, among others. As described above, thiscontrol signaling may be referred to as native domain control signaling.

In one example, data and information (e.g., such as a state variable)may be communicated between a control device and other devices via thenetwork interface 330. For instance, playback zone and zone groupconfigurations in the native media playback system may be received by acontrol device from a playback device, another control device, oranother network device, or transmitted by the control device to anotherplayback device or control device via the network interface 330. In somecases, the other network device may be another control device.

d. Example VLI Devices

FIG. 4 is a functional block diagram illustrating certain aspects of aselected one of the VLI devices 104 of the media playback system 100 ofFIG. 1. As noted above, a VLI device 104 may implement a timing domaindifferent than that of a native domain playback device 102. In variousaspects, a VLI device may include certain playback and/or controlfunctionality that is similar to that of the native media playbacksystem, while other functionality may be different than and/orunavailable to the VLI media playback system. In other words, some VLIdevices may be configured to perform specific functions such as controlor playback, while others are general purpose and capable of performingeither. As such the VLI device shown in FIG. 4 may include componentsthat are generally similar to certain components of the playback devicesand control devices shown above, such as a processor 412, softwarecomponents 414, memory 416, audio processing components 418, audioamplifiers 420, microphones 424, and a network interface 430, containedwithin a housing 438.

Example general purpose VLI devices include, for example, an iPhone™,iPad™ or any other smart phone, tablet or network device (e.g., anetworked computer such as a PC or Mac™. Generally, a general purposeVLI device is capable of operating as a VLI sender to a VLI receiver. Ageneral purpose network device may become a general purpose VLI devicevia installation of the VLI controller 428, which may provide controlsfor playback and/or control functionality in the VLI domain. A controldevice 103 that operates as a VLI sender may be referred to herein as aVLI device 104 when referring to its VLI domain functionality. A controldevice 103 that is not configured to operate as a VLI sender, such as acontrol device that does not have a VLI controller installed, is notreferred to as a VLI device 104.

e. Example User Interfaces

FIGS. 5A and 5B are example user interfaces in the form of nativecontrol interfaces 5A and 5B (collectively “control interface 526”) inaccordance with aspects of the disclosure. As noted above, one or moreadditional or alternate user interfaces, may be provided via acontroller app, such as a VUI. In any case, native control interface(s)of, e.g., a control device 103 may be configured to facilitate useraccess and control of the native media playback system. As anillustrative example, the control interfaces 526 a and 526 b shown inFIGS. 5A and 5B may be presented via the native controller 327 (FIG.3A). Referring to FIGS. 5A and 5B together, the control interface 526includes a playback control region 542, a playback zone region 543, aplayback status region 544, a playback queue region 546, and a sourcesregion 548. The control interface 526 and the respective functions ofthe native control controller 527 as shown and described below are justone example of user controls that may be provided via a network devicesuch as the control device shown in FIG. 3 and accessed by users tocontrol a media playback system such as the native media playback systemof system 100. Other control interfaces of varying formats, styles, andinteractive sequences may alternatively be implemented on one or morenetwork devices to provide comparable control access to a media playbacksystem.

The playback control region 542 (FIG. 5A) may include selectable (e.g.,by way of touch or by using a cursor) icons to cause playback devices ina selected playback zone or zone group to play or pause, fast forward,rewind, skip to next, skip to previous, enter/exit shuffle mode,enter/exit repeat mode, enter/exit cross fade mode. The playback controlregion 542 may also include selectable icons to modify equalizationsettings, and playback volume, among other possibilities.

The playback zone region 543 (FIG. 5B) may include representations ofplayback zones within the native media playback system. The playbackzones regions may also include representation of zone groups, such asthe Dining Room+Kitchen zone group, as shown. In some embodiments, thegraphical representations of playback zones may be selectable to bringup additional selectable icons to manage or configure the playback zonesin the media playback system, such as a creation of bonded zones,creation of zone groups, separation of zone groups, and renaming of zonegroups, among other possibilities.

For example, as shown, a “group” icon may be provided within each of thegraphical representations of playback zones. The “group” icon providedwithin a graphical representation of a particular zone may be selectableto bring up options to select one or more other zones in the mediaplayback system to be grouped with the particular zone. Once grouped,playback devices in the zones that have been grouped with the particularzone will be configured to play audio content in synchrony with theplayback device(s) in the particular zone. Analogously, a “group” iconmay be provided within a graphical representation of a zone group. Inthis case, the “group” icon may be selectable to bring up options todeselect one or more zones in the zone group to be removed from the zonegroup. Other interactions and implementations for grouping andungrouping zones via a user interface such as the native controlinterface 526 are also possible. The representations of playback zonesin the playback zone region 543 (FIG. 5B) may be dynamically updated asplayback zone or zone group configurations are modified.

The playback status region 544 (FIG. 5A) may include graphicalrepresentations of audio content that is presently being played,previously played, or scheduled to play next in the selected playbackzone or zone group. The selected playback zone or zone group may bevisually distinguished on the control interface, such as within theplayback zone region 543 and/or the playback status region 544. Thegraphical representations may include track title, artist name, albumname, album year, track length, and other relevant information that maybe useful for the user to know when controlling the media playbacksystem via the native control interface 526.

The playback queue region 546 may include graphical representations ofaudio content in a playback queue associated with the selected playbackzone or zone group. In some embodiments, each playback zone or zonegroup may be associated with a playback queue containing informationcorresponding to zero or more audio items for playback by the playbackzone or zone group. For instance, each audio item in the playback queuemay comprise a uniform resource identifier (URI), a uniform resourcelocator (URL) or some other identifier that may be used by a playbackdevice in the playback zone or zone group to find and/or retrieve theaudio item from a local audio content source or a networked audiocontent source, possibly for playback by the playback device.

In one example, a playlist may be added to a playback queue, in whichcase information corresponding to each audio item in the playlist may beadded to the playback queue. In another example, audio items in aplayback queue may be saved as a playlist. In a further example, aplayback queue may be empty, or populated but “not in use” when theplayback zone or zone group is playing continuously streaming audiocontent, such as Internet radio that may continue to play untilotherwise stopped, rather than discrete audio items that have playbackdurations. In an alternative embodiment, a playback queue can includeInternet radio and/or other streaming audio content items and be “inuse” when the playback zone or zone group is playing those items. Otherexamples are also possible.

When playback zones or zone groups are “grouped” or “ungrouped,”playback queues associated with the affected playback zones or zonegroups may be cleared or re-associated. For example, if a first playbackzone including a first playback queue is grouped with a second playbackzone including a second playback queue, the established zone group mayhave an associated playback queue that is initially empty, that containsaudio items from the first playback queue (such as if the secondplayback zone was added to the first playback zone), that contains audioitems from the second playback queue (such as if the first playback zonewas added to the second playback zone), or a combination of audio itemsfrom both the first and second playback queues. Subsequently, if theestablished zone group is ungrouped, the resulting first playback zonemay be re-associated with the previous first playback queue, or beassociated with a new playback queue that is empty or contains audioitems from the playback queue associated with the established zone groupbefore the established zone group was ungrouped. Similarly, theresulting second playback zone may be re-associated with the previoussecond playback queue, or be associated with a new playback queue thatis empty, or contains audio items from the playback queue associatedwith the established zone group before the established zone group wasungrouped. Other examples are also possible.

With reference still to FIGS. 5A and 5B, the graphical representationsof audio content in the playback queue region 546 (FIG. 5B) may includetrack titles, artist names, track lengths, and other relevantinformation associated with the audio content in the playback queue. Inone example, graphical representations of audio content may beselectable to bring up additional selectable icons to manage and/ormanipulate the playback queue and/or audio content represented in theplayback queue. For instance, a represented audio content may be removedfrom the playback queue, moved to a different position within theplayback queue, or selected to be played immediately, or after anycurrently playing audio content, among other possibilities. A playbackqueue associated with a playback zone or zone group may be stored in amemory on one or more playback devices in the playback zone or zonegroup, on a playback device that is not in the playback zone or zonegroup, and/or some other designated device. Playback of such a playbackqueue may involve one or more playback devices playing back media itemsof the queue, perhaps in sequential or random order.

FIG. 6 is an example VLI control interface 626 of in accordance withaspects of the disclosure. Similar to the control interface presented bya native control application, such as the control interface 526 shown inFIGS. 5A and 5B, the control interface(s) of a VLI device 104 may beconfigured to facilitate user access, control, and/or playback of thenative media playback system. For example, as shown in FIG. 5, thecontrol interface 626 of the VLI controller 428 (FIG. 4) may includeseveral similar regions as the control interface 526 (FIGS. 5A and 5B)presented via the native controller 327 (FIG. 3). For instance, thecontrol interface 526 of the VLI controller 428 includes a playbackcontrol region 642 and playback status region 644, which may begenerally similar to the playback control region 542 (FIG. 5A) and theplayback status region 544 (FIG. 5A), respectively.

The control interface 626 presented by the VLI controller 428 alsoincludes a VLI group region 443. As shown, the VLI group region 443includes a list of available VLI compatible devices within the nativemedia playback system and the VLI media playback system. In theillustrated example, the VLI devices are identified as “Bedroom,”“Master Bedroom,” “Phone,” and “Laptop,” which correspond to therespective VLI devices 104 a-e shown in FIG. 1. The VLI compatibledevices within the native media playback system (each identified with anasterisk) are associated with certain native playback devices 102 orzones. For example, the Living Room may be associated with playbackdevices 102 a, 102 b, 102 g, and 102 i; the Balcony may be associatedwith playback device 102 c; the Dining Room may be associated withplayback device 102 e; the Kitchen may be associated with playbackdevice 102 h; and the Office may be associated with playback device 102d.

Notably, the playback device 102 f shown in the Bathroom in FIG. 1 isnot presented on the VLI control interface 426. In some implementations,certain playback devices 102 (such as the playback device 102 f) mightnot support becoming VLI receivers or handling VLI signaling, such aslegacy devices, which might have hardware incompatibilities. Withinexamples, playback device(s) 102 and VLI device(s) 104 may advertisetheir availability using discovery packets via the LAN provided byrouter 106.

Upon selection of one or more playback device(s) 102 and/or VLIdevice(s) 104 in the VLI group region on a particular VLI device 104,the particular VLI device 104 creates a VLI session and forms a VLIgroup of the selected playback device(s) 102 and/or VLI device(s) 104.The particular VLI device 104 becomes the VLI sender for the new VLIsession. Other playback device(s) 102 and/or VLI device(s) 104 are VLIreceivers, which receive playback and control information from the VLIsender.

f. Example Audio Content Sources

Turning back to FIG. 5A, the sources region 548 (FIG. 5A) may includegraphical representations of selectable audio content sources and voiceassistant services. The audio sources in the sources region 548 may beaudio content sources from which audio content may be retrieved andplayed by the selected playback zone or zone group. One or more playbackdevices in a zone or zone group may be configured to retrieve forplayback audio content (e.g., according to a corresponding uniformresource identifier (URI) or uniform resource locator (URL) for theaudio content) from a variety of available audio content sources. In oneexample, audio content may be retrieved by a playback device directlyfrom a corresponding audio content source (e.g., a line-in connection).In another example, audio content may be provided to a playback deviceover a network via one or more other playback devices or networkdevices.

Example audio content sources may include a memory of one or moreplayback devices 102 such as the native or VLI media playback systems ofFIG. 1, local music libraries on one or more network devices (such as acontrol device, a network-enabled personal computer, or anetworked-attached storage (NAS), for example), streaming audio servicesproviding audio content via the Internet (e.g., the cloud), or audiosources connected to the native or VLI media playback systems via aline-in input connection on a playback device or network device, amongother possibilities.

In some embodiments, audio content sources may be regularly added orremoved from a media playback system such as the media playback system100 of FIG. 1. In one example, an indexing of audio items may beperformed whenever one or more audio content sources are added, removedor updated. Indexing of audio items may involve scanning foridentifiable audio items in all folders/directory shared over a networkaccessible by playback devices in the media playback system, andgenerating or updating an audio content database containing metadata(e.g., title, artist, album, track length, among others) and otherassociated information, such as a URI or URL for each identifiable audioitem found. Other examples for managing and maintaining audio contentsources may also be possible.

Example techniques described herein involve implementing the virtualline-in as another possible audio source for the native media playbacksystem. In contrast to other audio sources noted above, the virtualline-in is not selectable within a native domain user interface (e.g.,the sources region 548 of the native control interface 526). Instead,the virtual line-in is selected as an audio source for one or moreplayback device(s) 102 by selecting those playback devices 102 using aVLI domain control interface.

Within examples, the virtual line-in source is implemented as a UPnPservice. In such an implementation, each operation has a parameter(e.g., a first parameter) that identifies the type of virtual line-in.This allows the native media playback system to support multiple virtualline-in types, such as multiple media playback systems each using theirown domains or other types of input that the native media playbacksystem may handle using the virtual line-in implementation describedherein, such as a Bluetooth® audio stream.

III. Example VLI Group Control and Audio Distribution

a. Example Group Configurations

FIG. 7A is a functional block diagram illustrating example control andaudio distribution within a VLI group that includes the native domainplayback device 102 e. In this example, the VLI device 104 is the VLIsender, which functions to provide audio to the VLI receiver(s), andwhich in this example is the playback device 102 e. The VLI device 104that creates the VLI group becomes the VLI sender. The VLI device 104may create the group using any suitable control interface such as theexample control interface of the VLI controller 428 shown above or a VUI(e.g., via a voice command such as “Play David Bowie on Dining Room,”where the Dining Room zone corresponds to playback device 102 e as shownin FIG. 1).

As shown in FIG. 7A, the VLI sender provides an audio stream to theplayback device 102 e in the VLI domain. This VLI domain signaling isreceived at a virtual line-in block 750 e, which operates as aninterface between the VLI domain of the VLI device 104 and the nativedomain of the playback device 102. Generally, as noted above, the VLIand native domain signaling is transmitted via a network, such as theLAN provided by router 106 (FIG. 1).

The virtual line-in block 750 e converts the VLI domain audio streamfrom the VLI sender to a native domain audio stream and passes thenative domain audio stream to the channel sink 754 e. The channel sink754 e decodes the native domain audio stream and passes it to the audiostage (not shown in the FIG. 7A example) for output. In one aspect,since the channel sink 754 e receives the audio stream using nativedomain signaling, the channel sink 754 e can process the audio stream inthe same way it would process an audio stream that originated in thenative domain. In a related aspect, the conversion performed by thevirtual line-in 750 e facilitates interoperability between the VLIdomain audio stream and the native domain channel sink 754 e.

Depending on the encoding format of the VLI domain audio stream, the VLIreceiver may transcode the VLI domain audio stream into an uncompressedformat. For example, if the VLI domain audio stream is encoded in anencoding format that is not supported by the native domain decoder ofthe channel sink 754 e, the virtual line-in 750 e decodes the audiostream to an uncompressed format (e.g., PCM). This configuration may usemore bandwidth in distributing audio to downstream group members (notshown in the FIG. 7A example), but allows for greater compatibility.Conversely, if the VLI domain audio stream is encoded in an encodingformat supported by the native domain, then decoding is not performeduntil the channel sink 754 e. This configuration may have the advantageof being more bandwidth efficient, as the audio stream uses lessbandwidth when distributed in compressed format, especially inconfigurations that include multiple downstream group members.

The virtual line-in 750 e also handles metadata from the VLI sender. Insome implementations, the virtual line-in 750 e extracts metadata fromthe audio stream and passes the metadata in the native domain to theAVTransport 752 e. Alternatively, the VLI sender may send the metadatain a separate data stream using VLI domain control signaling. Theplayback device 102 e in FIG. 7A may be designated a native domain groupcoordinator as described below. Native domain functions of the nativedomain group coordinator include distribution of native domain audio andcontrol information (including metadata) to native group members (notshown in FIG. 7A), as well as receiving native domain controlinformation from native domain group members and control devices 103.These functions are carried out in the native domain by the AVTransport752 a.

In the example of FIG. 7A, since it is the only native playback device102 in the current VLI group, the playback device 102 e is necessarilythe native domain group coordinator. In effect, the playback device 102e is a native domain group coordinator for a native domain synchronygroup that includes only the playback device 102 e. The playback device102 e is effectively distributing audio and control information toitself as the native domain group coordinator. In this case, theplayback device 102 e need not distribute native domain audio andcontrol information (including metadata) to native group members untilsuch group members are later added. As such, in alternativeimplementations, a native domain group coordinator might not necessarilybe designated when a single native domain playback device 102 is in aVLI group.

Since the AVTransport 752 e receives the metadata using native domainsignaling, the AVTransport 752 e can process the metadata in the sameway it would process metadata from an audio stream that originated inthe native domain. That is, the AVTransport 752 e distributes metadataof the currently playing audio stream (which is received from the VLIsender during a VLI session) to native domain group members and controldevices 103. The native controller 327 on the control device 103receives the metadata and updates the playback status region 544 (FIG.5A) to reflect the audio content currently being played by the VLIgroup.

The native controller 327 on the control device 103 is also a source ofbackchannel control. That is, control commands received via the nativecontrol controller 327 on the control device 103 (e.g., via the playbackcontrol region 542) are passed back to the AVTransport 752 e of thegroup coordinator using native domain control signaling as shown in FIG.7A. The AVTransport 752 e passes these control commands to the virtualline-in 750 e, which converts the native domain control commands to VLIdomain control commands that the VLI sender can understand. Forinstance, the virtual line-in 750 e may convert the native domaincontrol commands to equivalent VLI domain API function calls.

The virtual line-in 750 e transmits these VLI domain commands back tothe VLI sender. The VLI sender then responds to the commands. Forinstance, in response to a skip forward command, the VLI sender startsstreaming the next song. As another example, in response to a volumeincrease or decrease command, the VLI sender sends a VLI domain commandto increase or decrease volume back to the VLI receivers(s). This VLIdomain command is carried out by the virtual line-in 750 e and alsoconverted to a native domain command for distribution to native domaingroup members via the AVTransport 752 e. Notably, even though thecommand may have originated via the native domain control controller327, the command is not carried out until it is received back from theVLI sender, which is the audio and control master of the VLI group.

FIG. 7B is a functional block diagram illustrating example control andaudio distribution within a VLI group that includes the playback device102 e and the playback device 102 h. Again, in this example, the VLIdevice 104 is the VLI sender, which, as noted above, functions toprovide audio to the VLI receiver(s), which in this example is theplayback device 102 e. The VLI device 104 may create this VLI groupusing any suitable control interface such as the example controlinterface of the VLI controller 428 shown above (e.g., by selectingLiving Room and Dining Room in the VLI group region 443 or a VUI (e.g.,via a voice command such as “Play David Bowie on Dining Room and LivingRoom”).

As shown in FIG. 7B, as audio and control master of the VLI group, theVLI sender provides an audio and control signaling to another VLIreceiver that has been added as a VLI domain group member of the VLIgroup (which is playback device 102 h in this example). The virtualline-in 750 e operates in the same manner as described in the exampleshown in FIG. 7A. The virtual line-in 750 h of the playback device 102 hoperates in a similar manner.

Notably, in addition to being VLI domain group members (VLI receivers),the playback device 102 e and the playback device 102 h are also nativedomain group members. Within example implementations, playback devices102 that are joined into a VLI domain group may automatically form anative domain group. Such auto-grouping may facilitate interoperabilitywith native domain control devices 103 and playback devices 102, as thenative domain grouping will be recognizable to native domain devices. Asnoted above, under native domain grouping, one playback device 102 willfunction as a group coordinator (which is playback device 102 e in thisexample) while the other playback devices will function as groupmembers.

Due to the native domain grouping, native domain group members (e.g.,playback device 102 h) may implement a control backchannel to the VLIsender through the native domain group coordinator (e.g., playbackdevice 102 e) as shown in FIG. 7B. This control backchannel may beimplemented in addition to, or as an alternative to, the backchannelimplemented through the virtual line-in of each VLI group member. Underthis configuration, native domain control signaling from a group memberis processed by the group coordinator in the same way as native domaincontrol signaling from a control device 103, as described above inconnection with FIG. 7A.

FIG. 7C is a functional block diagram illustrating example control andaudio distribution within a VLI group that includes the playback device102 h. This example is intended to demonstrate the flexibility of thevirtual line-in implementation. In this example, the VLI sender createda VLI group that included playback device 102 e and then playback wastransferred to playback devices 102 h and 102 d using native domaincontrol. For instance, such a transfer may involve the playback devices102 d and 102 h forming a native domain group with playback device 103 eusing the native controller 327. Then, using native domain control, theplayback devices 102 e is deselected from the native domain group,thereby creating the configuration shown in FIG. 7C.

To continue playback from the VLI sender, the playback device 102 econtinues to operate as VLI receiver, as it was the only VLI receiver inthe VLI group. However, instead of operating as a VLI receiver foritself, the playback device 102 e operates as a VLI receiver on behalfof the playback device 102 h, which becomes the group coordinator of thenative domain group when the playback device 102 e leaves the nativedomain group. Since the playback devices 102 e is no longer in thenative domain group (and no longer functioning as the group coordinatoror playing back audio), the AVTransport 752 e and Channel Sink 754 e arede-activated, as shown. Then, the playback devices 102 h and 102 d carryout synchronous playback using native domain signaling, also as shown.

FIG. 7D is a simplified functional block diagram illustrating examplecontrol and audio distribution within a VLI group that includes both VLIdevices 104 and playback devices 102 of the native media playbacksystem. In particular, the VLI group includes the playback devices 102 eand 102 h, as well as any number of VLI devices 104. In this example,the VLI device 104 a is the VLI sender. The VLI device 104 a may createthis VLI group using any suitable control interface such as the examplecontrol interface of the VLI controller 428 shown above (e.g., byselecting Kitchen, Dining Room, and one or more of the VLI devices suchas Bedroom or Laptop in the VLI group region 643 or a VUI (e.g., via avoice command such as “Play The Modern Lovers on Kitchen, Dining Room,Laptop, and Bedroom”).

In addition to the playback devices 102 e and 102 h, which are VLIreceivers in the VLI group, the example configuration shown in FIG. 7Dalso shows the playback device 102 f in a native domain grouping withthe playback devices 102 e and 102 h. Notably, the playback device 102 fis not in the VLI group. As such, the playback device 102 f is not a VLIreceiver and instead exchanges native domain audio and control signalingwith the group coordinator of the native domain group. As noted above,the playback device 102 f may be an example of a native playback devicethat is a legacy or other device with incompatibilities that do notallow it to become a VLI receiver. Alternately, the playback device maybe a native playback device (e.g., playback device 102 d) that iscapable of but not designated as a VLI receiver in the exampleimplemented in FIG. 7D.

b. Example Native Group Interactions

As noted above, selection of one or more playback devices 102 and/or VLIdevices 104 using a VLI domain user interface creates a VLI session andforms a VLI domain synchrony group among the selected devices. Forinstance, if Living Room is selected using the VLI controller, the VLIsender creates a VLI session with a VLI group that includes the playbackdevice 102 e as a VLI receiver, as shown in FIG. 7A. If the playbackdevice 102 e is in any native domain group, the playback device 102 e isremoved from this group when joined into the VLI domain group.

Continuing the example above, if another playback device 102 is selectedusing a VLI domain user interface, this playback device 102 is added tothe VLI group as a VLI receiver. For instance, as shown in FIG. 7B, theplayback device 102 h is a second VLI receiver. If the playback device102 h is in any native domain group, the playback device 102 e isremoved from this group when joined into the VLI domain group. Both VLIreceivers receive audio and control signaling in the VLI domain from theVLI sender.

Moreover, when two or more playback devices 102 are joined into the sameVLI group, these playback devices automatically form a native domaingroup. Automatic grouping may be implemented using a state variableindicating the group ID of the VLI group. This group ID may representthe VLI sender, perhaps by way of the audio stream originating from theVLI sender. As described above, the devices of the native media playbacksystem may share status information by sharing state variables in adistributed fashion with each player maintaining the current values ofstate variables of each playback device 102 within the native mediaplayback system. When the group IDs of two or more playback devices 102match (which occurs when they are part of the same VLI group and arereceiving the same audio stream), the native media playback systemautomatically groups these playback devices into a native domain groupusing native domain signaling.

In some implementations, automatic native domain grouping is performedby native group coordinators. That is, native group coordinators monitorthe group IDs for the native players in the native media playbacksystem. When the group ID of a native group coordinator matches thegroup ID of another native group coordinator, the native groupcoordinator may initiate grouping with the other native groupcoordinator. If these native group coordinators are in synchrony groupswith group members, these group members are moved into the automaticallyformed group by their respective group coordinators. In alternativeimplementations, the automatic grouping can be performed by groupmembers or native controllers, among other examples.

When automatically forming the native domain group, the native mediaplayback system assigns one playback device 102 to be the groupcoordinator and the other playback devices to be group members. As notedabove, the native domain group coordinator distributes audio and controlsignaling to the group members. If the native domain group is a stereopair or surround sound configuration, the preferred group coordinatormay be, e.g., the left channel of the stereo pair or the center channelof the surround sound configuration. Other examples are possible aswell.

When a playback device 102 is de-selected, the playback device 102 isremoved from the VLI group. Since that playback device 102 is no longerreceiving the same audio stream from the VLI sender as the other VLIgroup members, its group ID will no longer match the group IDs of theother VLI group members, which causes the native media playback systemto remove it from the native domain group as well. If the VLI receiverthat is also the group coordinator of the native domain group is removedfrom the VLI group, the native media playback system assigns another VLIreceiver to be the group coordinator. When the last remaining playbackdevice 102 in a VLI group is de-selected, the VLI session ends.

In the event that all playback device(s) 102 in a VLI group arede-selected at the same time or the VLI session otherwise ends, thenative media playback system may automatically maintain the nativedomain group. The VLI device 104 may de-select all playback device(s)102 in a VLI group at the same time by selecting another playback targetusing the VLI group region 443, perhaps by selecting “Play on thisdevice” or the like. Alternatively, the VLI device 104 may de-select allplayback device(s) 102 using a VUI (e.g., via a voice command such as“Play David Bowie on Bedroom,” where the Bedroom zone corresponds to theVLI device 104 a.

In some examples, the VLI sender may transmit a signal to a groupcoordinator of the native media playback system to indicate that all ofthe native playback devices have been deselected at the same time. Inadditional or alternate embodiments, a native domain group is maintainedfor any playback devices 102 that were de-selected from a VLI group viathe VLI controller 428 within a given window of time from when the firstplayback device was removed from the VLI group. For example, if two ormore playback devices 102 are de-selected from a VLI group within agiven window of time (e.g., a 3-second window of time), the group ofde-selected devices may be maintained in a native group.

In contrast, devices that are de-selected outside of this window of timeare not automatically joined to the native domain group. For instance,if a VLI group comprising a VLI device 104 and the playback devices 102corresponding to the Living Room, Kitchen, and Dining Room zones has theLiving Room and Kitchen zones de-selected within a three second windowof time from when the first zones was de-selected, the Living Room andthe Kitchen zones would together form a native domain group. If theDining Room zone is later removed from the VLI group (i.e., outside ofthe window of time), the Dining Room zone would not become part of thenative domain Living Room and Kitchen group.

In some cases, a phone call or other event involving audio on the VLIsender may interrupt the VLI session. Such events may take control ofthe audio pipeline on the VLI sender. These events cause the VLI sessionto be terminated and then automatically restarted when the event ends.

As noted above, a native domain user interface (such as a GUI or VUI)may interact with the playback device(s) 102 in the VLI group, asdemonstrated with the native controller 327 on the control device 103 inFIGS. 7A-7D. Example operations involve adding and removing one or moreplayback device(s) 102 from the native domain group (which wasautomatically formed when the VLI group was formed). Removing the groupcoordinator from the native domain group causes the native mediaplayback system to assign a new VLI receiver (if available) as the groupcoordinator.

Other example operations include changing the audio source of the nativedomain group to a non-VLI source. When the audio source of the nativedomain group is changed to a non-VLI source, the playback device(s) 102in the VLI group are removed from the VLI group. However, the nativemedia playback system maintains the native domain group and startsplaying back audio from the new audio source.

IV. Example VLI Timing Distribution

FIG. 8A is a functional block diagram illustrating example timingdistribution within a native domain synchrony group that includesplayback devices 102 e and 102 h. In this example, the playback devices102 e and 102 h are not members of a VLI group. The playback device 102e is assigned as the group coordinator, and the playback device 102 h isa group member. As the group coordinator, the playback device 102 eprovides audio and timing information to the group member(s) (i.e.,playback device 102 h), which enables the group members (playback device102 h) to synchronize its playback to that of the group coordinator.Notably, the playback devices 102 e and 102 h are independently clockedvia a DAC clock 860 e and a DAC clock 860 h, respectively.

In operation, the sound input device (SID) of the group coordinator(here, the SID/ADC 861 e of the playback device 102 e) receives adigital audio stream or analog signal. If the received audio is analog,the SID/ADC 861 e digitizes the analog signal into a digital audiostream. In some examples, the SID and ADC may be separate components. Inpractice, they are often implemented on the same physical CODEC chip andso are shown by way of example as a single component.

The SID/ADC 861 e processes the audio content at a rate set by the DACclock 860 e. Ultimately, the DAC clock 860 e sets the clock for thenative domain group. That is, group members (e.g., the playback device102 h) match their clocks (either physically or logically) to the DACclock of the group coordinator (i.e., the DAC clock 860 e).

The audio input of the group coordinator (i.e., the audio input 862 e)distributes the audio to each channel sink 863 of the native domainsynchrony group (i.e., the channel sinks 863 e and 863 h). Each channelsink 863 of the native domain synchrony group decodes the audio content,which is then converted to analog and outputted by the signal outputdevice and analog-to-digital converter (SOD/DAC 864), as shown in FIG.8A.

To facilitate synchronous playback, a native domain clock such as theDAC clock of the group coordinator provides a reference or basis of thetiming information of the timing source for the native domain timingserver 865 (i.e., the native domain timing server 865 e). The nativedomain timing server 865 implements a network protocol for clocksynchronization such as network time protocol (NTP), simplified networktime protocol SNTP, real-time transport protocol (RTP) or precision timeprotocol (PTP), among others. The native domain timing server 865 edistributes timing information according to one of these protocols tothe native domain client 866 h thereby providing the playback device 102h with a signal representing the current clock time of the groupcoordinator.

Each native group member can assess a timing differential between themaster clock and a given group member's DAC clock to periodically adjustits respective DAC clock or adjust a sampling rate (depending on theselected corrective mechanism), with the adjustment ultimately achievingsynchrony when audio is played back among devices with independentlyclocked DACs. In particular, this timing signal representing the timedomain of the group coordinator is used by the sync 867 of each groupmember of the native domain synchrony group to keep audio playback ofthe group member in synchronization with audio playback by the groupcoordinator. In one implementation, the VCXO of the sync 867 h uses thetiming signal to “discipline” the DAC clock 860 h of the playback device102 h by speeding it up or slowing it down to match the DAC clock 860 e.In an alternative implementation, the AsyncSRC of the sync 867 uses thetiming signal to cause the channel sink 863 h logically insert or removesamples from the audio stream in order for its playback rate to matchthat of the group coordinator. As noted above, this playback rate is setby the DAC clock 860 e.

Certain components that exist in both devices but are not in use in thisexample are omitted from the block diagram. Generally, each playbackdevice 102 can be assumed to have the same or similar components.Different playback devices 102 may implement similar functions usingdifferent hardware (e.g., newer and/or different chips).

Turning now to FIG. 8B, shown is a functional block diagram illustratingexample timing distribution within a VLI group that includes theplayback device 102 e. In this example, the playback device 102 h is ina native domain group with the playback device 102 e. In this example,the VLI device 104 is the timing master. As such, the playback device102 e uses VLI domain synchronization to synchronize with the VLI device104. However, the playback device 102 h uses native domainsynchronization to synchronize with the playback device 102 e. At thesame time, the native domain synchronization by the group coordinator(the playback device 102 e) is derived from the VLI domainsynchronization. As such, the playback devices 102 e and 102 h areultimately synchronized to the VLI time domain of the VLI device 104.

The playback devices 102 of the native media playback system areconfigured to synchronize to any of a number of clock sources. As such,the timing master can be either a VLI device 104 or a playback device102 (e.g., a VLI receiver). The timing master selected based on variousfactors. In an example hierarchy, the VLI sender is selected to be thetiming master unless the VLI sender is battery-powered. In that case, toavoid battery drain associated with operating as the timing master, anAC (wall-powered) VLI device 104 is selected as the timing master. If noAC powered VLI device 104 is in the VLI group, then a playback device102 is selected as the timing master.

As shown in FIG. 8B, the VLI domain timing server 869 of the VLI device104 distributes timing information according to a network protocol forclock synchronization thereby providing the playback device 102 e with asignal representing the VLI time domain of the timing master. In someexamples, the network protocol for clock synchronization used by the VLIdomain timing server is the same protocol (e.g., NTP, SNTP, RTP or PTP,among others) as used by the native domain timing server and client(s).However, even if they use the same protocol, the respective clocks ofthe VLI domain and the native domain are not synchronized, as theultimate source of the clock in each domain is different.

Ultimately, the signal representing the VLI time domain is one input tothe audio input 862 of each playback device 102 in the VLI group.Another input to the audio input 862 of each playback device 102 in theVLI group (i.e., the VLI receivers) includes the audio stream from theVLI sender, which in this example is the VLI device 104. However, theVLI sender and the VLI timing domain master need not be the same device,as noted above.

The audio input 862 e of the playback device 102 e processes audiocontent from the VLI sender at a rate set by the CPU clock 859 e andpasses the audio content to the channel sink 863 e, as shown in FIG. 8B.Since the playback device 102 e is also the native domain groupcoordinator of a native domain group that include the playback device102 h as a group member, the audio input 862 e distributes the audio tothe channel sink 863 of the each native domain group member (i.e., thechannel sink 863 h). Each channel sink 863 decodes the audio content,which is then converted to analog and outputted by the signal outputdevice and digital-to-analog converter (SOD/DAC 864), as shown in FIG.8B.

To facilitate synchronous playback, the audio input 862 e of theplayback device 102 e also generates a skew signal representing theerror between the CPU clock 859 e and the clock of the VLI domain (whichthe audio input 862 e receives from the VLI domain timing server 869).For instance, the skew signal may represent a number of audio samplesthat CPU clock 859 e is ahead of or behind the VLI domain clock. Forinstance, consecutive elements of the skew signal might be +3 samples,−2 samples, −1 samples, +2 samples.

The virtual clock 870 e uses the CPU clock 859 e and the skew signal toderive a virtual clock signal synchronized to the VLI domain masterclock, which becomes the master clock in the native domain. That is, incontrast to FIG. 8A where the DAC clock 860 of the group coordinator isthe native domain timing master, in this example, the native domaintiming master is the virtual clock. Since the virtual clock issynchronized to the VLI domain master clock, the native timing domainbecomes synchronized to the VLI timing domain when using the virtualclock.

To convert the virtual clock 870 e into a native domain format, thevirtual clock 870 e is used to seed a native domain timing server 865 e,which distributes native domain timing information to a native domaintiming client 866 e on the group coordinator itself, as well as a nativedomain timing client(s) on each native domain group member (i.e., nativedomain timing client 866 h). From that point, the sync 867 of eachplayback device 102 synchronizes the audio output of each playbackdevice using the same native domain technique as described with respectto the group member (the playback device 102 h) in the FIG. 7B example.In other words, the path following the native domain timing client 866on each playback device 102 is the same as the path following the nativedomain timing client 866 in the FIG. 7A example. Yet, in the FIG. 7Bexample, the master clock is ultimately the VLI domain timing masterinstead of the DAC clock of the native domain group coordinator.

FIG. 8C shows a functional block diagram illustrating a variation on theFIG. 8B example in which the playback device 102 e is the VLI domaintiming master. As such, the playback device 102 e implements a VLIdomain time server 869 e that distributes VLI domain timing informationto the VLI sender, as well as any number of VLI receivers, including VLIdevices 104 and playback devices 102.

Further, like the FIG. 8B example, in the FIG. 8C example, the playbackdevice 102 h is in a native domain group with the playback device 102 e.However, with the exception of the VLI domain timing originating withthe VLI domain timing server 869 e (instead of the VLI domain timingserver 869 on the VLI device 104), all functionality is the same, asshown in FIG. 8C.

Turning now to FIG. 9A, shown is a simplified functional block diagramillustrating example timing distribution within VLI and native domaingroups. The VLI group includes VLI devices 104 d and 104 e as a VLIsender and receiver, respectively, as well as playback devices 102 a,102 b, and 102 g as VLI receivers. In addition to playback devices 102a, 102 b, and 102 g, the native domain group includes the playbackdevice 102 d, which was added to the native domain group using nativedomain signaling. As such, the playback device 102 d is not a VLIreceiver of the VLI group. The playback device 102 a is the groupcoordinator of the native domain group.

In the FIG. 9A example, the playback device 102 a is the VLI timingmaster. As such, the playback device 102 a distributes VLI timinginformation to each VLI receiver in the VLI group, which includes theVLI devices 104 d and 104 e, as well as the playback devices 102 b and102 g. The playback devices 102 b and 102 g operating as VLI receiversprocess the audio from the VLI sender and the VLI domain timinginformation from the VLI timing master in a similar manner as playbackdevice 102 e in the FIG. 8B example. In this example, the VLI domainmedia playback system utilizes the PTP protocol, so VLI domain timinginformation is labeled PTP.

The playback device 102 a processes the processes the audio from the VLIsender and the VLI domain timing information in a similar manner asplayback device 102 e in the FIG. 8C example, as the VLI domain timingserver is implemented in the playback device 102 a. Moreover, theplayback device 102 a distributes native domain audio and timinginformation to the playback device 102 d in a similar manner as theplayback device 102 e and playback device 102 h in the FIG. 8C example.In this example, the native domain media playback system utilizes theSNTP protocol, so VLI domain timing information is labeled SNTP.

FIG. 9B shows another simplified functional block diagram illustratingexample timing distribution within VLI and native domain groups. The VLIgroup includes VLI devices 104 b and 104 c as a VLI receiver and sender,respectively, as well as playback devices 102 a, 102 b, and 102 g as VLIreceivers. In addition to playback devices 102 a, 102 b, and 102 g, thenative domain group includes the playback device 102 d, which was addedto the native domain group using native domain signaling. As such, theplayback device 102 d is not a VLI receiver of the VLI group. Theplayback device 102 a is the group coordinator of the native domaingroup.

In the FIG. 9B example, the VLI device 104 b is the VLI timing master.As such, the VLI device 104 b distributes VLI timing information to eachVLI receiver in the VLI group, which includes the VLI devices 104 b and104 c, as well as the playback devices 102 a, 102 b and 102 g. Theplayback devices 102 a, 102 b and 102 g operating as VLI receiversprocess the audio from the VLI sender and the VLI domain timinginformation from the VLI timing master in a similar manner as playbackdevice 102 e in the FIG. 8B example.

Moreover, the playback device 102 a distributes native domain audio andtiming information to the playback device 102 d in a similar manner asthe playback device 102 e and playback device 102 h in the FIG. 8Bexample. The “legacy” playback device 102 d can be added to the nativedomain synchrony group using the native controller 326 (e.g., viaplayback zone region 543 (FIG. 5B)). In this way, the native playbackdevice 102 d can synchronize playback with the VLI group even though theplayback device 102 d is not a VLI receiver. In other words, nativedomain group members can synchronize using native domain audio andtiming information to a native domain group coordinator that isconfigured as a VLI receiver.

V. Example Techniques for Improved Interoperability Between VLI andNative Media Playback Systems

As indicated above, to facilitate interoperability between the VLI mediaplayback system and the native domain media playback system, a playbackdevice 102 may convert VLI domain control signaling to native domaincontrol signaling and vice versa. However, in some cases, there mightnot be an equivalent function or command in the VLI domain for eachnative domain command. Similarly, the VLI media playback system mayimplement certain operations in different ways.

To illustrate, in one example, the VLI media playback system and nativemedia playback systems implement mute in different ways. For instance,the VLI media playback system implements mute by lowering volume to apre-determined inaudible volume level (e.g., −144 dB). In contrast, thenative media playback system implements “true” mute, whereby it'spossible to have a non-zero volume level with mute enabled with the mutestate taking precedence over the group volume level. Within examples,either type of mute command mutes all grouped devices.

In a first example, a VLI session starts with the native domain mute setto disabled. If the VLI sender sets the volume level to thepre-determined inaudible volume level using the VLI domain controller327, the VLI sender transmits VLI commands to each VLI receiver settingthe group volume level to the pre-determined inaudible volume level. TheVLI device(s) 104 receiving this VLI domain command carry out thecommand literally, by setting their group volume level to thepre-determined inaudible volume level.

However, if a given playback device 102 (operating as a VLI receiver)receives this VLI domain command, the playback device 102 does not carryout the command literally. Instead, the playback device 102 enables thenative domain mute, stores the current native domain volume level, andsets the native domain volume to zero. Enabling the native domain mutehas the side effective of also muting any playback device 102 in anative domain group with the given playback device 102 via the nativedomain control signaling described above. In addition, storing thecurrent native domain volume level allows the playback device(s) 102 tore-establish the same pre-mute volume level when mute is disabled. Yetfurther, setting the native domain volume to zero cause the volumeslider of any native domain controller 327 to match the volume controlof the VLI domain control app 328.

If the given playback device 102 (operating as a VLI receiver) receivesa native domain mute command, the playback device 102 does not carry outthe command literally. Instead, the playback device 102 sends a proxiedvolume control command (as discussed in section III for instance) to setthe volume level to the pre-determined inaudible volume level. Uponreceiving this command, the VLI sender relays this command back to theplayback device 102. In response, the playback device 102 enables thenative domain mute, stores the current native domain volume level, andsets the native domain volume to zero, in the same manner as describedabove.

While in the VLI domain mute state, the playback device 102 may receiveVLI or native domain commands to change the group volume level to anon-zero level. If the playback device 102 receives a native domaincommand to set the volume to a given level (e.g., via a volume slider ofthe native controller 327 or volume button on the playback device 102),the playback device 102 disables the native domain mute state and setsthe native domain volume level to the given level. If the playbackdevice 102 receives a VLI domain command to set the volume to a givenlevel (e.g., via a volume slider of the VLI control controller 428), theplayback device 102 disables the native domain mute state and sets thenative domain volume level to the given level.

In a second example, a VLI session starts with the native domain muteset to enabled. As the VLI session starts, the VLI receivers adjust tothe volume level set by the VLI sender. Unless this volume level is thepre-determined inaudible volume level, the playback device 102 disablesthe native domain mute and sets the native domain volume level to thegiven level. If the playback device 102 receives a native domain commandto disable mute, the playback device 102 disables the native domain muteand keeps the native domain volume level at the volume level set by theVLI sender. If the playback device 102 receives a VLI domain command toset the group volume level to a non-zero volume level, the playbackdevice 102 disables the native domain mute and sets the native domainvolume level to the non-zero volume level.

If the VLI session ends with the native domain mute enabled, theplayback device 102 retains the current native domain mute state andnative domain volume level.

VI. Example Methods

Implementations 1000 and 1100 shown in FIGS. 10 and 11, respectivelypresent example embodiments of techniques described herein. Theseexample embodiments that can be implemented within an operatingenvironment including, for example, the media playback system 100 ofFIG. 1, one or more of the playback device 200 of FIG. 2, one or more ofthe control device 300 of FIG. 3, one or more of the VLI devices of FIG.4, as well as other devices described herein and/or other suitabledevices. Further, operations illustrated by way of example as beingperformed by a media playback system can be performed by any suitabledevice, such as a playback device or a control device of a mediaplayback system. Implementation 1000 and 1100 may include one or moreoperations, functions, or actions as illustrated by one or more ofblocks shown in FIGS. 10 and 11. Although the blocks are illustrated insequential order, these blocks may also be performed in parallel, and/orin a different order than those described herein. Also, the variousblocks may be combined into fewer blocks, divided into additionalblocks, and/or removed based upon the desired implementation.

In addition, for the implementations disclosed herein, the flowchartsshow functionality and operation of one possible implementation ofpresent embodiments. In this regard, each block may represent a module,a segment, or a portion of program code, which includes one or moreinstructions executable by a processor for implementing specific logicalfunctions or steps in the process. The program code may be stored on anytype of computer readable medium, for example, such as a storage deviceincluding a disk or hard drive. The computer readable medium may includenon-transitory computer readable medium, for example, such ascomputer-readable media that stores data for short periods of time likeregister memory, processor cache, and Random Access Memory (RAM). Thecomputer readable medium may also include non-transitory media, such assecondary or persistent long term storage, like read only memory (ROM),optical or magnetic disks, compact-disc read only memory (CD-ROM), forexample. The computer readable media may also be any other volatile ornon-volatile storage systems. The computer readable medium may beconsidered a computer readable storage medium, for example, or atangible storage device. In addition, for the implementations disclosedherein, each block may represent circuitry that is wired to perform thespecific logical functions in the process.

a. Example Methods for VLI Group Control and Audio Distribution

As discussed above, embodiments described herein involve VLI groupcontrol and audio distribution. FIG. 10 illustrates an exampleimplementation 1000 of a method by which a system distributes controland audio signals within a VLI and native groups.

At block 1002, the implementation 1000 involves receiving a command toplay back audio content. For instance, a first VLI device 104 configuredas a VLI sender of a VLI group may receive, via an input interface ofthe first VLI device, a command to play back audio content. Toillustrate, referring back to FIG. 7A, the VLI device 104 is configuredas a VLI sender of a VLI group and may receive a command to play backaudio content via the VLI controller 428.

Alternatively, the VLI device 104 may receive the command to play backaudio content via a VUI. In such examples, the VLI device 104 mayreceive, via a microphone array, a voice command to play back the audiocontent. The voice command may also select the devices in the VLI groupby referring to certain VLI devices 104 or native playback devices 102by reference to their name (e.g., a zone name, such as “Kitchen” or“Living Room”).

In some examples, the command to play back audio content may also createa VLI session. Creating a VLI session may involve selecting one or moreVLI devices 104 and/or native playback devices 102 and selecting audiocontent for the VLI group to play back. In some implementations, the VLIdevice 104 receiving the command to play back audio content becomes theVLI sender of the VLI group. That is, the particular VLI device 104receiving the command starts the VLI session and accordingly becomes theVLI sender of the VLI group. Other selected devices are then configuredas VLI receivers of the VLI group.

At block 1004, the implementation 1000 involves streaming the audiocontent from one or more servers. For example, the first VLI device 104may stream, via a network interface of the first VLI device, streamingthe audio content from one or more servers, such as one or more serversof a streaming audio service or from an audio server on the VLI device104 itself.

At block 1006, the implementation 1000 involves sending a VLI domainaudio stream representing the streamed audio content to one or more VLIreceivers of the VLI group. For instance, the VLI device 104 may send,via the network interface of the first VLI device, a VLI domain audiostream representing the streamed audio content to one or more VLIreceivers of the VLI group. To illustrate, in FIG. 7A, the VLI device104 sends a VLI domain audio stream to the playback device 102 e as VLIsender. As another example, in FIG. 7D, the VLI device 104 a sends a VLIdomain audio stream to playback devices 102 e and 102 h.

At block 1008, the implementation 1000 involves receiving the VLI domainaudio stream representing the streamed audio content. For example, afirst native playback device configured as a first VLI receiver of theVLI group may receive, via a network interface of the first nativeplayback device, the VLI domain audio stream representing the streamedaudio content.

At block 1010, the implementation 1000 involves converting the VLIdomain audio stream to a native domain audio stream. For instance, thefirst native playback device may convert, via one or more processors,the VLI domain audio stream from the first VLI device to a native domainaudio stream. To illustrate, referring back to FIG. 7A, the playbackdevice 102 e may convert the VLI domain audio stream from the VLI device104. The playback device 102 e may perform such a conversion using thevirtual line-in 750 e, among other examples.

At block 1012, the implementation 1000 involves decoding the nativedomain audio stream. For example, the first native playback device maydecode, via the one or more processors, the native domain audio stream.By way of example, referring back to FIG. 7A, the playback device 102 emay decode the native domain audio stream. As one example, the playbackdevice 102 e may perform such decoding using the channel sink 863 e.

At block 1014, the implementation 1000 involves playing back the decodednative domain audio stream. The first native playback device may playback the decoded native domain audio stream via an audio stage thatincludes one or more amplifiers (e.g., audio amplifier(s) 220 of theplayback device 102 shown in FIG. 2) that drive one or more speakers(e.g., speaker(s) 222 shown in FIG. 2).

The first native playback device may perform additional functions invarious roles as a VLI receiver and/or native domain group coordinator.For instance, the first native playback device may extract metadataassociated with the streamed audio content from the VLI domain audiostream. As a VLI receiver, the first native playback device may use thisextracted metadata to provide information about the audio content in theVLI domain audio stream to VLI control interfaces.

As the native domain group coordinator, the first native playback devicemay send, or otherwise distribute, native domain signaling representingthe extracted metadata to one or more native domain control devices. Forinstance, referring back to FIG. 7A, the playback device 103 e may sendnative domain signaling representing the extracted metadata to thecontrol device 103. Upon receiving such native domain signaling, thecontrol device 103 may update the native controller 327 to display anindication of the metadata. For example, the control device 103 mayupdate control interfaces such controller interfaces 526 a and 526 b inFIGS. 5A and 5B, respectively, to provide information on the currentlyplaying audio content by way of the extracted metadata.

In some instances, the native control device 103 sends native domainplayback commands to the first native playback device when user input isprovided to the native control device 103 (e.g., via the nativecontroller 327). When the first native playback device receives a nativedomain playback command, the first native playback device might notcarry out that command. Instead, the first native playback device mayconvert the native domain playback command to a corresponding VLI domaininstruction and send the VLI domain instruction to the first VLI device.For instance, referring again to FIG. 7A, when the playback device 103 ereceives a native domain playback command from the native control device103, the playback device 103 e converts that native domain playbackcommand to a corresponding VLI domain instruction and sends the VLIdomain instruction to the VLI device 104 (i.e., the VLI sender). Then,the VLI device 104, as the VLI sender, based on the VLI domaininstruction, causes the VLI group (including the first native playbackdevice as a VLI receiver) to carry out a VLI domain playback commandcorresponding to the native domain playback command. As noted above,example playback commands in both the VLI and native domains includetransport control (e.g., play/pause, skip forward/backward, fastforward/rewind, stop, etc.) and volume control (e.g., volume up/down andmute).

In an example, the native domain playback command is a particular nativedomain playback command that, when carried out by the VLI group, causesthe VLI group to play back a second audio track. Such a command might bea skip forward or backward, or a command to play the second audio track(e.g., a selection of the second audio track from a queue or playlist).In such an example, the first VLI device (e.g., VLI device 104) maycarry out the VLI domain playback command corresponding to the nativedomain playback command by streaming, via the network interface of thefirst VLI device, the second audio track from the one or more serversand sending, via the network interface of the first VLI device, a VLIdomain audio stream representing the second audio track to the firstnative playback device to the VLI receivers of the VLI group.

The first native playback device (as a VLI receiver) then receives theVLI domain audio stream representing the second audio track. Then, thefirst native playback device converts the VLI domain audio streamrepresenting the second audio track to a native domain audio streamrepresenting the second audio track. The first native playback devicethen handles the converted audio stream as it would any native domainaudio stream. As described above, the first native playback devicedecodes the native domain audio stream representing the second audiotrack and plays back the decoded native domain audio stream via itsaudio stage.

In another example, the native domain playback command is a particularnative domain playback command that, when carried out by the VLI group,causes the VLI group to adjust volume (e.g., a volume up/down or mutecommand). In this example, the first VLI device (e.g., VLI device 104)may carry out the VLI domain playback command corresponding to thenative domain playback command by sending the VLI domain playbackcommand to one or more VLI receivers of the VLI group. The VLI receivers(e.g., the first native playback device) receive this VLI domainplayback command and adjust volume according to the VLI domain playbackcommand.

In some examples, the VLI group includes a second VLI receiver, whichmay be a second VLI device or a second native playback device. Forinstance, the playback device 102 b in FIG. 9A is an example of a secondnative playback device configured as a second VLI receiver and the VLIdevice 104 e is an example of a second VLI device configured as a secondVLI receiver. In each case, the second VLI receiver receives the VLIdomain audio stream representing the streamed audio content from the VLIsender. The second native playback device converts the VLI domain audiostream to the native domain audio stream and then decodes and plays backthe native domain audio stream. In contrast, the second VLI devicedecodes and plays back the VLI domain audio stream. In each case, theplayback is in synchrony with the other VLI receivers.

When the first native playback device is a native domain groupcoordinator of a native domain synchrony group that includes a secondnative playback device configured as a native domain group member, thefirst native playback device may perform certain functions to facilitateconcurrent synchronous playback by the VLI group and the native domainsynchrony group. For instance, the native domain group coordinator maydistribute the native domain audio stream to one or more native domaingroup members for playback by the one or more native domain groupmembers. In addition, the native domain group coordinator may convertthe VLI domain playback commands to corresponding native domain playbackcommands and distribute the native domain playback command to the nativedomain group member(s) of the native domain synchrony group. Since thenative domain group member(s) are not part of the VLI group, suchfunctions facilitate the native domain group member(s) performingplayback in the same way as the VLI group members. As an example, inFIG. 7D, the playback device 102 e is a native domain group coordinatorof a native domain synchrony group that includes the playback device 102f as a group member.

Within examples, the first native playback device need not be the nativedomain group coordinator and a second native playback device can insteadbe configured as the native domain group coordinator. For instance,referring to FIG. 7C, the playback device 102 h is configured as thegroup coordinator of a native domain synchrony group that includes theplayback device 102 f as a native domain group member. Notably, theplayback device 102 h is not configured as a VLI receiver. The playbackdevice 102 h receives the native domain audio stream from the playbackdevice 102 e, which is configured as a VLI receiver.

In further examples, the first VLI device is configured as a VLIreceiver in addition to a VLI sender. As VLI receiver, the first VLIdevice plays back the audio content in synchrony with the other VLIreceivers. In particular, the first VLI device decodes the VLI domainaudio stream and plays back the decoded VLI domain audio stream insynchrony with the first native playback device via an audio stage ofthe first VLI device.

b. Example Methods for VLI Group Timing

As discussed above, embodiments described herein involve VLI grouptiming to facilitate synchronization of audio playback with nativeplayback devices. FIG. 11 illustrates an example implementation 1100 ofa method by which a system distributes control and audio signals withina VLI and native groups.

At block 1102, the implementation 1100 involves receiving a VLI domainaudio stream representing audio content. For instance, a first nativeplayback device configured as a VLI receiver of a VLI group may receivea VLI domain audio stream from a VLI sender of the VLI group. An examplefirst native playback device is the playback device 102 e shown in FIGS.8B and 8C and an example VLI sender is the VLI device 104 also shown inFIGS. 8B and 8C.

The VLI sender may receive one or more commands to play back the audiocontent (and possibly to start a VLI session and to form a VLI groupthat includes the first native playback device) via a VUI controlinterface. Based on these command(s), the VLI sender streams the audiocontent from one or more servers and sends a VLI domain audio streamrepresenting the audio content to one or more VLI receivers of the VLIgroup. The first native playback device, as a VLI receiver of the VLIgroup, receives this VLI domain audio stream.

At block 1104, the implementation 1100 involves converting the VLIdomain audio stream to a native domain audio stream. For instance, thefirst native playback device may convert, via one or more processors,the VLI domain audio stream from the first VLI device to a native domainaudio stream. To illustrate, referring to FIG. 8B, the playback device102 e may convert the VLI domain audio stream from the VLI device 104 tothe native domain audio stream at a rate set by a device clock of thefirst native playback device. Example device clocks include the CPUclock 859 e and DAC clock 860 e. The playback device 102 e may performsuch a conversion using the virtual line-in 862 e, among other examples.

At block 1106, the implementation 1100 involves receiving a VLI domainclock signal. In some implementations, the first native playback devicereceives the VLI domain clock signal from a VLI domain timing server ona VLI device 104 such as the VLI sender. An example of thisconfiguration is shown in FIG. 8B. Alternatively, the first nativeplayback device receives the VLI domain clock signal from a VLI domaintiming server on the first native playback device. An example of thisimplementation is shown in FIG. 8C.

Within examples, the VLI group may select a VLI domain timing master toimplement the VLI domain server. In an example implementation, the VLIsource is selected as the VLI domain timing master when the VLI sourceis powered by an external AC power source. However, when the VLI sourceis powered by an internal battery, the VLI group may select anexternally powered VLI receiver, such as the first native playbackdevice or another VLI device 104 configured as a VLI receiver. Thishierarchy avoids relatively high power usage (and associated batterydrain) that results from implementing a VLI domain timing server anddistributing the VLI domain clock signal to VLI group members.

At block 1108, the implementation 1100 involves deriving a virtual clocksignal synchronized to the VLI domain clock signal. The first nativeplayback device may derive the virtual clock signal based on a skewsignal representing the error between the device clock and the VLIdomain clock signal. For example, referring again to FIG. 8B, theplayback device 102 e may generates a skew signal representing the errorbetween the CPU clock 859 e and the VLI domain clock signal from the VLIdevice 104 (which the audio input 862 e receives from the VLI domaintiming server 869). The skew signal may represent a number of audiosamples that CPU clock 859 e is ahead of or behind the VLI domain clock.For instance, consecutive elements of the skew signal might be +3samples, −2 samples, −1 samples, +2 samples.

The virtual clock 870 e uses the difference between the CPU clock 859 eand the VLI domain clock signal represented by the skew signal to derivea virtual clock signal synchronized to the VLI domain master clock. Forinstance, the virtual clock 870 e may discipline the device clock withthe skew signal to generate the virtual clock signal synchronized to theVLI domain clock signal. As shown in FIG. 8B, the virtual clock 870 edisciplines the CPU clock 859 e with the skew signal to generate thevirtual clock signal.

At block 1110, the implementation 1100 involves seeding a native domaintiming server with the derived virtual clock signal. For example, thefirst native playback device may provide the derived virtual clocksignal as a seed to a native domain timing server to generate a nativedomain clock signal synchronized to the VLI domain clock signal. Toillustrate, referring again to FIG. 8B, the playback device 103 eprovides the virtual clock 870 e as a seed to the native domain timingserver 865 e.

During native operation, by contrast, the seed to the native domaintiming server 865 e is the device clock (e.g., the CPU clock 859 e orthe DAC clock 860 e). As such, when the VLI group is formed, the firstnative playback device may switch the seed of the native domain timingserver from the device clock to the derived virtual clock signal.Likewise, when the VLI session ends (and the first native playbackdevice is removed from the VLI group), the first native device switchesthe seed of the native domain timing server from the derived virtualclock signal to the device clock.

At block 1112, the implementation 1000 involves decoding the nativedomain audio stream. For instance, the first native playback device maydecode, via the one or more processors, the native domain audio streamat a rate set by the native domain clock signal. Since the native domainclock signal is synchronized to the VLI domain clock signal, the firstnative playback device decodes the native domain audio stream at insynchrony with other VLI receivers. By way of example, referring againto FIG. 8B, the channel sink 863 e decodes the native domain audiostream from the audio input 862 e.

The first native playback device may decode the native domain audiostream at the rate set by the native domain clock signal in severaldifferent ways. In some examples, the first native playback devicedisciplines a digital-to-audio converter clock to the native domainclock signal synchronized to the VLI domain clock signal. In otherwords, as shown in FIG. 8B, the VCXO of the sync 867 e uses the nativedomain clock signal to “discipline” the DAC clock 860 e of the playbackdevice 102 e by speeding it up or slowing it down to match the nativedomain clock signal. Alternatively, the first native playback device mayinsert or remove samples from the native domain audio stream using thenative domain clock signal to cause a playback rate of the first nativeplayback device to match VLI domain clock signal. For example, theAsyncSRC of the sync 867 e uses the native domain clock signal to causethe channel sink 863 e logically insert or remove samples from the audiostream in order for its playback rate to match that of other VLI groupmembers.

At block 1114, the implementation 1000 involves playing back the decodednative domain audio stream. The first native playback device may playback the decoded native domain audio stream via an audio stage thatincludes one or more amplifiers (e.g., audio amplifier(s) 220 of theplayback device 102 shown in FIG. 2) that drive one or more speakers(e.g., speaker(s) 222 shown in FIG. 2).

The first native playback device may also be configured as a nativedomain group coordinator of a native domain synchrony group. In suchexamples, if the native domain synchrony group includes one or morenative domain group members, the first native playback devicedistributes, to the one or more native domain group members, the nativedomain audio stream and the native domain clock signal synchronized tothe VLI domain clock signal. An example of this is shown in FIG. 8B,where the playback device 102 e distributes the native domain audiostream and the native domain clock signal to the playback device 102 h.

A second native playback device configured as a native domain groupmember of the native domain synchrony group may perform functions tofacilitate synchronous playback with the native domain groupcoordinator. For instance, the second native playback device may receivethe native domain audio stream and the native domain clock signal. Thesecond native playback device may then decode the native domain audiostream at a rate set by the native domain clock signal and play back thedecoded native domain audio stream in synchrony with the first nativeplayback device.

In further examples, a second native playback device may be configuredas a second VLI receiver of the VLI group. In such examples, the secondnative playback device performs similar functions as the first nativeplayback device. That is, as the second VLI receiver, the second nativeplayback device, receives the VLI domain audio stream and converts theVLI domain audio stream to a second native domain audio stream at a rateset by a device clock of the second native playback device. The secondnative playback device also receives the VLI domain clock signal fromthe VLI domain timing server, derives its own virtual clock signalsynchronized to the VLI domain clock signal, and seeds its native domaintiming server with that virtual clock. Then, the second native playbackdevice decodes the native domain audio stream at a rate set by thesecond native domain clock signal and plays back the decoded nativedomain audio stream in synchrony with the first native playback device.An example of a second native playback device configured as a VLIreceiver is the playback device 102 b of FIG. 9A.

In some examples, the VLI group includes a second VLI device configuredas a VLI receiver. For instance, referring still to FIG. 9A, the VLIdevice 104 e is configured as a VLI receiver of the VLI group. As theVLI receiver of the VLI group, the VLI device 104 e receives the VLIdomain audio stream representing the streamed audio content and the VLIdomain clock signal. The VLI device 104 e decodes the VLI domain audiostream at the rate set by the VLI domain clock signal and plays back thedecoded VLI domain audio stream in synchrony with the other VLIreceivers.

In some cases, the first VLI device is configured as a VLI receiver inaddition to the VLI sender. In such examples, to facilitate synchronousplayback with the other VLI receivers, the first VLI device decodes theVLI domain audio stream at the rate set by the VLI domain clock signaland plays back the decoded VLI domain audio stream in synchrony with theother VLI receivers. The first VLI device may receive the VLI domainclock signal from the first native playback device (as illustrated inFIG. 9A) or an internal VLI domain timing server (as demonstrated inFIG. 9B).

VII. Conclusion

The description above discloses, among other things, various examplesystems, methods, apparatus, and articles of manufacture including,among other components, firmware and/or software executed on hardware.It is understood that such examples are merely illustrative and shouldnot be considered as limiting. For example, it is contemplated that anyor all of the firmware, hardware, and/or software aspects or componentscan be embodied exclusively in hardware, exclusively in software,exclusively in firmware, or in any combination of hardware, software,and/or firmware. Accordingly, the examples provided are not the onlyway(s) to implement such systems, methods, apparatus, and/or articles ofmanufacture.

(Feature 1) A method to be performed by one or more devices of a VLIgroup comprising a first native playback device configured as a firstVirtual Line In (VLI) receiver of the VLI group, wherein the VLI groupis configured to (i) receive via an input interface of a first VLIdevice, a command to play back audio content and (ii) send, via anetwork interface of the first VLI device, a VLI domain audio streamrepresenting the audio content to one or more VLI receivers of the VLIgroup, and wherein the method comprises receiving, via a networkinterface of the first native playback device, a VLI domain audio streamrepresenting the audio content; converting, via one or more processors,the VLI domain audio stream to a native domain audio stream at a rateset by a device clock of the first native playback device; receiving,from a VLI domain timing server, a VLI domain clock signal; deriving avirtual clock signal synchronized to the VLI domain clock signal;providing the derived virtual clock signal as a seed to a native domaintiming server to generate a native domain clock signal synchronized tothe VLI domain clock signal; decoding, via the one or more processors,the native domain audio stream at a rate set by the native domain clocksignal; and playing back the decoded native domain audio stream via anaudio stage of the first native playback device, the audio stage of thefirst native playback device comprising one or more amplifiers thatdrive one or more speakers.

(Feature 2) The method of feature 1, further comprising selecting a VLIdomain timing master to implement the VLI domain timing server, whereinthe VLI source is selected as the VLI domain timing master when the VLIsource is powered by an external AC power source; and wherein the firstVLI receiver is selected as the VLI domain timing master when the VLIsource is powered by an internal battery.

(Feature 3) The method of feature 1, wherein the first native playbackdevice is configured as a native domain group coordinator of a nativedomain synchrony group to perform further functions of the methodcomprising: distributing, to one or more native domain group members,(i) the native domain audio stream and (ii) the native domain clocksignal synchronized to the VLI domain clock signal, and wherein a secondnative playback device is configured as a native domain group member ofa native domain synchrony group to perform functions of the methodcomprising receiving the native domain audio stream and the nativedomain clock signal synchronized to the VLI domain clock signal;decoding, via one or more processors of the second native playbackdevice, the native domain audio stream at a rate set by the nativedomain clock signal; and playing back the decoded native domain audiostream via an audio stage of the second native playback device insynchrony with the first native playback device, the audio stage of thesecond native playback device comprising one or more amplifiers thatdrive one or more speakers.

(Feature 4) The method of feature 1, wherein deriving the virtual clocksignal synchronized to the VLI domain clock signal comprises generatinga skew signal representing error between the device clock of the firstnative playback device and the VLI domain clock signal; and generatingthe virtual clock signal synchronized to the VLI domain clock signalfrom the device clock and the skew signal.

(Feature 5) The method of feature 1, wherein decoding the native domainaudio stream at the rate set by the native domain clock signal comprisesdisciplining a digital-to-audio converter clock to the native domainclock signal synchronized to the VLI domain clock signal.

(Feature 6) The method of feature 1, wherein decoding the native domainaudio stream at the rate set by the native domain clock signal comprisesinserting or removing samples from the native domain audio stream usingthe native domain clock signal to cause a playback rate of the firstnative playback device to match VLI domain clock signal.

(Feature 7) The method of feature 1, wherein providing the derivedvirtual clock signal as the seed to the native domain timing servercomprises switching the seed of the native domain timing server from thedevice clock to the derived virtual clock signal when the VLI groupinitiates playback.

(Feature 8) The method of feature 7, further comprising switching theseed of the native domain timing server from the derived virtual clocksignal to the device clock when the VLI group is terminated.

(Feature 9) The method of feature 1, wherein a second native playbackdevice is configured as a second VLI receiver of the VLI group toperform functions of the method comprising receiving, via a networkinterface of the second native playback device, the VLI domain audiostream representing the audio content; converting, via one or moreprocessors, the VLI domain audio stream to a second native domain audiostream at a rate set by a device clock of the second native playbackdevice; receiving, from the VLI domain timing server, the VLI domainclock signal; deriving a second virtual clock signal synchronized to theVLI domain clock signal; providing the derived second virtual clocksignal as a seed to a native domain timing server of the second nativeplayback device to generate a second native domain clock signalsynchronized to the VLI domain clock signal; decoding, via the one ormore processors, the native domain audio stream at a rate set by thesecond native domain clock signal; and playing back the decoded nativedomain audio stream in synchrony with the first native playback devicevia an audio stage of the second native playback device, the audio stageof the second native playback device comprising one or more amplifiersthat drive one or more speakers.

(Feature 10) The method of feature 1, wherein a second VLI deviceconfigured as a second VLI receiver of the VLI group to performfunctions of the method comprising receiving, via a network interface ofthe second VLI device, (i) the VLI domain audio stream representing thestreamed audio content and (ii) the VLI domain clock signal; decodingthe VLI domain audio stream at the rate set by the VLI domain clocksignal; and playing back the decoded VLI domain audio stream insynchrony with the first native playback device via an audio stage ofthe second VLI device, the audio stage of the second VLI devicecomprising one or more amplifiers that drive one or more speakers.

(Feature 11) The method of feature 1, wherein the input interface of thefirst VLI device comprises a touch-sensitive graphical display, andwherein receiving the command to play back audio content comprises:displaying, on the touch-sensitive graphical display, a user interfaceof a VLI control application, the user interface including controls toselect audio content for playback and controls to select a playbackdevice; and receiving, via the user interface of the VLI controlapplication, input data representing selection of the audio content forplayback and selection of the first native playback device, whereinselection of the audio content for playback on the first VLI deviceconfigures the first VLI device as the VLI source of the VLI group andwherein selection of the first native playback device causes the firstVLI device to configure the first native playback device as the firstVLI receiver of the VLI group.

(Feature 12) The method of feature 1, wherein the first VLI device isconfigured as a second VLI receiver of the VLI group to performfunctions of the method comprising: receiving the VLI domain clocksignal; decoding the VLI domain audio stream at the rate set by the VLIdomain clock signal; and playing back the decoded VLI domain audiostream in synchrony with the first native playback device via an audiostage of the first VLI device, the audio stage of the first VLI devicecomprising one or more amplifiers that drive one or more speakers.

(Feature 13) The method of feature 12, wherein the input interface ofthe first VLI device comprises a microphone array, and wherein receivingthe command to play back audio content comprises: receiving, via themicrophone array, a voice command to play back the audio content on thefirst VLI device and the first native playback device; and in responseto the voice command, configuring the first VLI device as the VLI sourceof the VLI group and the first native playback device as the first VLIreceiver of the VLI group.

(Feature 14) A system configured to perform the method of any offeatures 1-13.

(Feature 15) A tangible, non-transitory computer-readable medium havingstored therein instructions executable by one or more processors tocause a device to perform the method of any of features 1-13.

(Feature 16) A playback device configured to perform the method of anyof features 1-13.

(Feature 17) A method to be performed by a first VLI device configuredas a VLI source of a VLI group and a first native playback deviceconfigured as a first VLI receiver of the VLI group, the methodcomprising the first VLI device receiving, via an input interface of thefirst VLI device, a command to play back audio content; streaming, via anetwork interface of the first VLI device, the audio content from one ormore servers; and sending, via the network interface of the first VLIdevice, a VLI domain audio stream representing the streamed audiocontent to one or more VLI receivers of the VLI group. The methodfurther comprising the first native playback device receiving, via anetwork interface of the first native playback device, the VLI domainaudio stream representing the streamed audio content; converting, viaone or more processors, the VLI domain audio stream to a native domainaudio stream; decoding, via the one or more processors, the nativedomain audio stream; and playing back the decoded native domain audiostream via an audio stage of the first native playback device, the audiostage of the first native playback device comprising one or moreamplifiers that drive one or more speakers.

(Feature 18) The method of feature 17, further comprising the firstnative playback device receiving metadata associated with the streamedaudio content from (a) the VLI domain audio stream or (b) a VLI domaindata stream and sending, via the network interface of the first nativeplayback device to one or more native domain control devices, nativedomain signaling representing the extracted metadata. The method furthercomprising one or more native domain control devices receiving, viarespective network interfaces of the one or more native domain controldevices, the native domain signaling representing the received metadataand displaying, in respective native domain control applications, thereceived metadata.

(Feature 19) The method of feature 17, further comprising while playingback a first audio track of the decoded native domain audio stream,receiving a native domain playback command via (a) via the networkinterface of the first native playback device from a given native domaincontrol device or (b) via a user interface of the first native playbackdevice; converting the native domain playback command to a correspondingVLI domain instruction; and sending, via the network interface of thefirst native playback device, the VLI domain instruction to the firstVLI device. The method further comprising the first VLI device inresponse to the VLI domain instruction, causing, via the networkinterface of the first VLI device, the VLI group to carry out a VLIdomain playback command corresponding to the native domain playbackcommand.

(Feature 20) The method of feature 19, wherein the native domainplayback command is a particular native domain playback command that,when carried out by the VLI group, causes the VLI group to play back asecond audio track, and wherein causing the VLI group to carry out theVLI domain playback command corresponding to the native domain playbackcommand comprises: in response to the VLI domain instruction, streaming,via the network interface of the first VLI device, the second audiotrack from the one or more servers; and sending, via the networkinterface of the first VLI device, a VLI domain audio streamrepresenting the second audio track to the first native playback device.The method further comprising the first native playback devicereceiving, via the network interface of the first native playbackdevice, the VLI domain audio stream representing the second audio track;converting, via one or more processors, the VLI domain audio streamrepresenting the second audio track to a native domain audio streamrepresenting the second audio track; decoding the native domain audiostream representing the second audio track; and playing back, via theaudio stage of the first native playback device, the decoded nativedomain audio stream representing the second audio track.

(Feature 21) The method of feature 19, wherein the native domainplayback command is a particular native domain playback command that,when carried out by the VLI group, causes the VLI group to adjustvolume, and wherein causing the VLI group to carry out the VLI domainplayback command corresponding to the native domain playback commandcomprises: in response to the VLI domain instruction, sending, via thenetwork interface of the first VLI device, the VLI domain playbackcommand to one or more VLI receivers of the VLI group. The methodfurther comprising first native playback device receiving, via thenetwork interface of the first native playback device, the VLI domainplayback command; and adjusting volume according to the VLI domainplayback command.

(Feature 22) The method of feature 21, further comprising the firstnative playback device converting, via one or more processors, the VLIdomain playback command to a native domain playback command; anddistributing the native domain playback command to a native domain groupmember of a native domain synchrony group.

(Feature 23) The method of feature 17, further comprising a secondnative playback device receiving, via a network interface of the secondnative playback device, the VLI domain audio stream representing thestreamed audio content; converting, via one or more processors, the VLIdomain audio stream to the native domain audio stream; decoding thenative domain audio stream; and playing back the decoded native domainaudio stream in synchrony with the first native playback device via anaudio stage of the second native playback device, the second nativeplayback device comprising one or more amplifiers that drive one or morespeakers.

(Feature 24) The method of feature 23, further comprising the firstnative playback device distributing, via the network interface of thefirst native playback device, the native domain audio stream to one ormore native domain group members. The method further comprising a thirdnative playback device receiving, via a network interface of the thirdnative playback device, the native domain audio stream; decoding thenative domain audio stream; and playing back the decoded native domainaudio stream in synchrony with the first native playback device and thesecond native playback device via an audio stage of the second nativeplayback device, the audio stage of the second native playback devicecomprising one or more amplifiers that drive one or more speakers.

(Feature 25) The method of feature 17, further comprising the firstnative playback device distributing, via the network interface of thefirst native playback device, the native domain audio stream to one ormore native domain group members. The method further comprising a secondnative playback device receiving, via a network interface of the secondnative playback device, the native domain audio stream; decoding thenative domain audio stream; and playing back the decoded native domainaudio stream in synchrony with the first native playback device via anaudio stage of the second native playback device, the audio stage of thesecond native playback device comprising one or more amplifiers thatdrive one or more speakers.

(Feature 26) The method of feature 17, further comprising a secondnative playback device receiving, via a network interface of the secondnative playback device from the first native playback device, the nativedomain audio stream; receiving, via a network interface of the secondnative playback device from the first native playback device, the nativedomain audio stream; decoding the native domain audio stream; andplaying back the decoded native domain audio stream via an audio stageof the second native playback device, the audio stage of the secondnative playback device comprising one or more amplifiers that drive oneor more speakers. The method further comprising a third native playbackdevice receiving, via a network interface of the third native playbackdevice from the second native playback device, the native domain audiostream; decoding the native domain audio stream; and playing back thedecoded native domain audio stream in synchrony with the second nativeplayback device via an audio stage of the second native playback device,the audio stage of the second native playback device comprising one ormore amplifiers that drive one or more speakers.

(Feature 27) The method of feature 17, further comprising a second VLIdevice receiving, via a network interface of the second VLI device, theVLI domain audio stream representing the streamed audio content;decoding the VLI domain audio stream; and playing back the decoded VLIdomain audio stream in synchrony with the first native playback devicevia an audio stage of the second VLI device, the audio stage of thesecond VLI device comprising one or more amplifiers that drive one ormore speakers.

(Feature 28) The method of feature 17, wherein the input interface ofthe first VLI device comprises a touch-sensitive graphical display, andwherein receiving the command to play back audio content comprises:displaying, on the touch-sensitive graphical display, a user interfaceof a VLI control application, the user interface including controls toselect audio content for playback and controls to select a playbackdevice; and receiving, via the user interface of the VLI controlapplication, input data representing selection of the audio content forplayback and selection of the first native playback device, whereinselection of the audio content for playback on the first VLI deviceconfigures the first VLI device as the VLI source of the VLI group andwherein selection of the first native playback device causes the firstVLI device to configure the first native playback device as the firstVLI receiver of the VLI group.

(Feature 29) The method of feature 17, further comprising the first VLIdevice decoding the VLI domain audio stream; and playing back thedecoded VLI domain audio stream in synchrony with the first nativeplayback device via an audio stage of the first VLI device, the audiostage of the first VLI device comprising one or more amplifiers thatdrive one or more speakers.

(Feature 30) The method of feature 29, wherein the input interface ofthe first VLI device comprises a microphone array, and wherein receivingthe command to play back audio content comprises: receiving, via themicrophone array, a voice command to play back the audio content on thefirst VLI device and the first native playback device; and in responseto the voice command, configuring the first VLI device as the VLI sourceof the VLI group and the first native playback device as the first VLIreceiver of the VLI group.

(Feature 31) The method of feature 17, wherein the system furthercomprises a second native playback device, wherein the first nativeplayback device is configured as a native domain group coordinator of anative domain synchrony group to perform functions comprising: detectingthat a VLI group ID of the first native playback device matches a VLIgroup ID of the second native playback device, wherein the second nativeplayback device is configured as a second VLI receiver of the VLI group;and automatically forming a new native domain synchrony group with thesecond native playback device based on detecting that the VLI group IDof the first native playback device matches the VLI group ID of thesecond native playback device, wherein automatically forming the nativedomain synchrony group comprises updating one or more state variablesstored on the first native playback device and the second nativeplayback device to indicate that (a) one of the first and second nativeplayback devices is a native domain group coordinator of the new nativedomain synchrony group and (b) the other one of the first and secondnative playback devices is a native domain group member of the newnative domain synchrony group.

(Feature 32) The method of feature 17, further comprising the firstnative playback device receiving, via a network interface of the firstnative playback device, a VLI domain mute command; translating the VLIdomain mute command to one or more corresponding first native domainmute commands, wherein the one or more corresponding first native domainmute commands comprise: (i) enabling a native domain mute state on thefirst native domain playback device, (ii) storing a current nativedomain volume level of the first native domain playback device, and(iii) setting the native domain volume level to zero; and in response toreceiving the VLI domain mute command, carrying out the one or morecorresponding first native domain mute commands to perform the muteoperation on the first VLI receiver.

(Feature 33) The method of feature 17, wherein the first VLI devicecomprises the one or more servers.

(Feature 34) A system configured to perform the method of any offeatures 17-33.

(Feature 35) A tangible, non-transitory computer-readable medium havingstored therein instructions executable by one or more processors tocause a device to perform the method of any of features 17-33.

(Feature 36) A playback device configured to perform the method of anyof features 17-33.

The specification is presented largely in terms of illustrativeenvironments, systems, procedures, steps, logic blocks, processing, andother symbolic representations that directly or indirectly resemble theoperations of data processing devices coupled to networks. These processdescriptions and representations are typically used by those skilled inthe art to most effectively convey the substance of their work to othersskilled in the art. Numerous specific details are set forth to provide athorough understanding of the present disclosure. However, it isunderstood to those skilled in the art that certain embodiments of thepresent disclosure can be practiced without certain, specific details.In other instances, well known methods, procedures, components, andcircuitry have not been described in detail to avoid unnecessarilyobscuring aspects of the embodiments. Accordingly, the scope of thepresent disclosure is defined by the appended claims rather than theforgoing description of embodiments.

When any of the appended claims are read to cover a purely softwareand/or firmware implementation, at least one of the elements in at leastone example is hereby expressly defined to include a tangible,non-transitory medium such as a memory, DVD, CD, Blu-ray, and so on,storing the software and/or firmware.

We claim:
 1. A system comprising a first native playback deviceconfigured as a first Virtual Line In (VLI) receiver of a VLI group,wherein the VLI group is configured to (i) receive via an inputinterface of a first VLI device, a command to play back audio contentand (ii) send, via a network interface of the first VLI device, a VLIdomain audio stream representing the audio content to one or more VLIreceivers of the VLI group, and wherein the first native playback deviceis configured to perform functions as the VLI receiver of the VLI groupcomprising: receiving, via a network interface of the first nativeplayback device, the VLI domain audio stream representing the audiocontent; converting, via one or more processors, the VLI domain audiostream to a native domain audio stream at a rate set by a device clockof the first native playback device; receiving, from a VLI domain timingserver, a VLI domain clock signal; deriving a virtual clock signalsynchronized to the VLI domain clock signal; providing the derivedvirtual clock signal as a seed to a native domain timing server togenerate a native domain clock signal synchronized to the VLI domainclock signal; decoding, via the one or more processors, the nativedomain audio stream at a rate set by the native domain clock signal; andplaying back the decoded native domain audio stream.
 2. The system ofclaim 1, wherein the first native playback device is configured as anative domain group coordinator of a native domain synchrony group toperform functions comprising: distributing, to one or more native domaingroup members, (i) the native domain audio stream and (ii) the nativedomain clock signal synchronized to the VLI domain clock signal, whereinthe system further comprises a second native playback device configuredas a native domain group member of a native domain synchrony group toperform functions comprising: receiving the native domain audio streamand the native domain clock signal synchronized to the VLI domain clocksignal; decoding, via one or more processors of the second nativeplayback device, the native domain audio stream at a rate set by thenative domain clock signal; and playing back the decoded native domainaudio stream via an audio stage of the second native playback device insynchrony with the first native playback device.
 3. The system of claim1, wherein deriving the virtual clock signal synchronized to the VLIdomain clock signal comprises: generating a skew signal representingerror between the device clock of the first native playback device andthe VLI domain clock signal; and generating the virtual clock signalsynchronized to the VLI domain clock signal from the device clock andthe skew signal.
 4. The system of claim 1, wherein decoding the nativedomain audio stream at the rate set by the native domain clock signalcomprises: disciplining a digital-to-audio converter clock to the nativedomain clock signal synchronized to the VLI domain clock signal.
 5. Thesystem of claim 1, wherein decoding the native domain audio stream atthe rate set by the native domain clock signal comprises: inserting orremoving samples from the native domain audio stream using the nativedomain clock signal to cause a playback rate of the first nativeplayback device to match VLI domain clock signal.
 6. The system of claim1, wherein providing the derived virtual clock signal as the seed to thenative domain timing server comprises: switching the seed of the nativedomain timing server from the device clock to the derived virtual clocksignal when the VLI group initiates playback.
 7. The system of claim 6,wherein the first native playback device is configured as a nativedomain group coordinator of a native domain synchrony group to performfunctions comprising: switching the seed of the native domain timingserver from the derived virtual clock signal to the device clock whenthe VLI group is terminated.
 8. The system of claim 1, furthercomprising a second native playback device, the second native playbackdevice configured as a second VLI receiver of the VLI group to performfunctions comprising: receiving, via a network interface of the secondnative playback device, the VLI domain audio stream representing theaudio content; converting, via one or more processors, the VLI domainaudio stream to a second native domain audio stream at a rate set by adevice clock of the second native playback device; receiving, from theVLI domain timing server, the VLI domain clock signal; deriving a secondvirtual clock signal synchronized to the VLI domain clock signal;providing the derived second virtual clock signal as a seed to a nativedomain timing server of the second native playback device to generate asecond native domain clock signal synchronized to the VLI domain clocksignal; decoding, via the one or more processors, the native domainaudio stream at a rate set by the second native domain clock signal; andplaying back the decoded native domain audio stream in synchrony withthe first native playback device via an audio stage of the second nativeplayback device.
 9. The system of claim 1, further comprising a secondVLI device, the second VLI device configured as a second VLI receiver ofthe VLI group to perform functions comprising: receiving, via a networkinterface of the second VLI device, (i) the VLI domain audio streamrepresenting the streamed audio content and (ii) the VLI domain clocksignal; decoding the VLI domain audio stream at the rate set by the VLIdomain clock signal; and playing back the decoded VLI domain audiostream in synchrony with the first native playback device via an audiostage of the second VLI device.
 10. The system of claim 1, wherein thefirst VLI device is configured as a second VLI receiver of the VLI groupto perform functions comprising: receiving the VLI domain clock signal;decoding the VLI domain audio stream at the rate set by the VLI domainclock signal; and playing back the decoded VLI domain audio stream insynchrony with the first native playback device via an audio stage ofthe first VLI device.
 11. A method to be performed by a systemcomprising a first native playback device configured as a first VirtualLine In (VLI) receiver of a VLI group, wherein the VLI group isconfigured to (i) receive via an input interface of a first VLI device,a command to play back audio content and (ii) send, via a networkinterface of the first VLI device, a VLI domain audio streamrepresenting the audio content to one or more VLI receivers of the VLIgroup, and wherein the first native playback device is configured as theVLI receiver of the VLI group to perform steps of the method comprising:receiving, via a network interface of the first native playback device,the VLI domain audio stream representing the audio content; converting,via one or more processors, the VLI domain audio stream to a nativedomain audio stream at a rate set by a device clock of the first nativeplayback device; receiving, from a VLI domain timing server, a VLIdomain clock signal; deriving a virtual clock signal synchronized to theVLI domain clock signal; providing the derived virtual clock signal as aseed to a native domain timing server to generate a native domain clocksignal synchronized to the VLI domain clock signal; decoding, via theone or more processors, the native domain audio stream at a rate set bythe native domain clock signal; and playing back the decoded nativedomain audio stream.
 12. The method of claim 11, wherein the firstnative playback device is configured as a native domain groupcoordinator of a native domain synchrony group to perform steps of themethod comprising: distributing, to one or more native domain groupmembers, (i) the native domain audio stream and (ii) the native domainclock signal synchronized to the VLI domain clock signal, wherein thesystem further comprises a second native playback device configured as anative domain group member of a native domain synchrony group to performfunctions comprising: receiving the native domain audio stream and thenative domain clock signal synchronized to the VLI domain clock signal;decoding, via one or more processors of the second native playbackdevice, the native domain audio stream at a rate set by the nativedomain clock signal; and playing back the decoded native domain audiostream via an audio stage of the second native playback device insynchrony with the first native playback device.
 13. The method of claim11, wherein deriving the virtual clock signal synchronized to the VLIdomain clock signal comprises: generating a skew signal representingerror between the device clock of the first native playback device andthe VLI domain clock signal; and generating the virtual clock signalsynchronized to the VLI domain clock signal from the device clock andthe skew signal.
 14. The method of claim 11, wherein decoding the nativedomain audio stream at the rate set by the native domain clock signalcomprises: disciplining a digital-to-audio converter clock to the nativedomain clock signal synchronized to the VLI domain clock signal.
 15. Themethod of claim 11, wherein decoding the native domain audio stream atthe rate set by the native domain clock signal comprises: inserting orremoving samples from the native domain audio stream using the nativedomain clock signal to cause a playback rate of the first nativeplayback device to match VLI domain clock signal.
 16. The method ofclaim 11, wherein providing the derived virtual clock signal as the seedto the native domain timing server comprises: switching the seed of thenative domain timing server from the device clock to the derived virtualclock signal when the VLI group initiates playback.
 17. The method ofclaim 16, wherein the first native playback device is configured as anative domain group coordinator of a native domain synchrony group toperform steps of the method comprising: switching the seed of the nativedomain timing server from the derived virtual clock signal to the deviceclock when the VLI group is terminated.
 18. The method of claim 11,wherein the system further comprises a second native playback device,the second native playback device configured as a second VLI receiver ofthe VLI group to perform steps of the method comprising: receiving, viaa network interface of the second native playback device, the VLI domainaudio stream representing the audio content; converting, via one or moreprocessors, the VLI domain audio stream to a second native domain audiostream at a rate set by a device clock of the second native playbackdevice; receiving, from the VLI domain timing server, the VLI domainclock signal; deriving a second virtual clock signal synchronized to theVLI domain clock signal; providing the derived second virtual clocksignal as a seed to a native domain timing server of the second nativeplayback device to generate a second native domain clock signalsynchronized to the VLI domain clock signal; decoding, via the one ormore processors, the native domain audio stream at a rate set by thesecond native domain clock signal; and playing back the decoded nativedomain audio stream in synchrony with the first native playback devicevia an audio stage of the second native playback device.
 19. The methodof claim 11, wherein the system further comprises a second VLI device,the second VLI device configured as a second VLI receiver of the VLIgroup to perform steps of the method comprising: receiving, via anetwork interface of the second VLI device, (i) the VLI domain audiostream representing the streamed audio content and (ii) the VLI domainclock signal; decoding the VLI domain audio stream at the rate set bythe VLI domain clock signal; and playing back the decoded VLI domainaudio stream in synchrony with the first native playback device via anaudio stage of the second VLI device.
 20. The method of claim 11,wherein the first VLI device is configured as a second VLI receiver ofthe VLI group to perform steps of the method comprising: receiving theVLI domain clock signal; decoding the VLI domain audio stream at therate set by the VLI domain clock signal; and playing back the decodedVLI domain audio stream in synchrony with the first native playbackdevice via an audio stage of the first VLI device.